After an extensive sky survey covering the planetary systems of a wide range of mid- to high-mass long-lived stars, a number of interesting systems were identified. Although scientists have traditionally focussed on stars suitable for life, with some success, the decision was made to widen the parameters for consideration to larger and more luminous examples in order to prevent observer bias. In particular, a fairly large and hot star was located whose planetary atmospheres showed a number of interesting features. The star was named Sol.
Sol is on first examination not the ideal location for life-bearing worlds. The star itself is considerably more luminous, hotter and more short-lived than our own and there is a notable absence of planets in the habitable zone, occupied by asteroids in this system. Moreover, there is an unusual absence of any planets with the mass of Planet, and therefore moons such as our home world, where life can arise and evolve straightforwardly, are completely lacking. The problems with life arising in this system are multiple. The lifetime of the star is relatively short, the system inside the asteroid belt is above the boiling point of ammonia, which in any case tends to get broken down by the radiation.
In the inner system, there are a large number of moons, all of which are however not particularly hospitable to life. Although three of the four gas giants have large moons, only one has a substantial atmosphere and is too cold for life as we know it to thrive or even appear there. Even so, this proved to be the most hospitable environment and a base was established there from which to mount missions to the other worlds in the system. None of the moons were at all promising. However, just out of curiosity, it was suggested that we investigate the inner system, in spite of its presumed hostility to life.
The situation did not at first appear very promising. There was only one relatively large satellite and even it was too small to maintain an atmosphere. The fourth planet had two small asteroid-sized moons which were even less promising, and the inner two planets had none at all. Two of the planets were large, and of these the outer planet was the host for the single large satellite, although it was considerably smaller than Planet itself. The fourth planet is close to our own world in size but is less dense and has very little to no ammonia on its surface and a tenuous atmosphere incompatible with the existence of most liquids.
Although slightly less hostile than the second planet, the host planet attracted attention because of its rather unpromising moon. It was found that, most improbably, the moon was of such a size and distance from the planet that it would perfectly cover the planet’s star from some locations on the planet, a situation which may well be unique in our Galaxy. This attracted attention to the solid surface of said planet, henceforth referred to as Sol III.
Sol III is a large, hot and rocky planet with a highly corrosive atmosphere and a surface largely covered in an expanse of molten dihydrogen monoxide rock, a substance henceforth referred to by its systematic standard name of oxidane. Runaway exothermic chemical reactions periodically occur on the surface where the likes of thunderstorms and volcanic eruptions trigger destructive processes which it might be thought would completely transform the surface. However, it has been found that in many cases this reaction can be limited by the presence of the liquid oxidane, which prevents dioxygen and the compounds in question coming into contact. Although the atmosphere is mainly (di)nitrogen, over a fifth of it consists of free dioxygen at sea level, becoming ozone some distance above the surface. Although the moon shows captured rotation, Sol III does not, rotating once every 24 hours. This has the consequence of causing the molten rock to flood the margins of the isolated land promontories twice every rotation. Any organism able to survive the extreme heat of most of the solid planetary surface unfortunate enough to find itself in such a location would be swiftly boiled to death by such events. Even away from the lava fields, liquid rock often falls from the sky, so there is little respite elsewhere on the planet.
There are exceptions to these conditions. There is a small area on the west side of one of the southern land promontories where this precipitation rarely or never takes place and many other regions close to the equator where it’s a relatively uncommon event, and these areas are free from the rivers and other bodies which make conditions so hazardous. The liquid is also quite corrosive and somewhat acidic compared to ammonia and tends to eat away at the solid surface of the planet. There are clouds of vaporised rock higher in the atmosphere which sometimes reach ground level. Near the poles the situation is slightly more hospitable, since these areas stay below oxidane’s melting point, and near the south pole temperatures are comfortable through most of the planet’s orbit and relatively normal crystallised oxidane.
Surface gravity is about triple our own, which would make it difficult to tolerate for long, and immersion in liquid would be one strategy to enable us to survive for long periods on the surface Sol is bluer than our own sun, with the result that the landscape, seascape and items within it have a blue tinge. This particularly applies to the lava plains dominating the surface and the sky when free of cloud. The higher gravity also flattens the solid surface, most of which is below the level of the lava, reducing the relief still further.
Considering the oxidane as a simple bulk substitute for our own ammonia, the chief difference between Sol III and our home moon is that the majority of the world is covered by an interconnected body of water, into which streams and rivers tend to feed, unlike our system of independently interconnected lake networks. Its mineral nature is emphasised by the presence in solution of many minerals, partly due to the strongly solvent properties of the liquid. More than half the solid surface is in permanent darkness and only just above oxidane’s melting point, though still far above the levels compatible with life as we know it. Also common here is a manifestation of the even hotter interior of the planet, also found on land, where even the silicate minerals melt and flow like ammonia. The silicate volcanism of Sol III, though, is physically still quite similar to our own oxidane volcanism, except that the volcanoes produced tend to be flatter and have less steep sides.
Technical terms have had to have been invented for the surface features of the planet. The lava fields are referred to by the arcane classical term “ocean”, and the giant island promontories as “continents”. Although the ocean is a single entity, there are also lakes on the surface which are not linked to them. These tend to be purer oxidane because of the reduced volume and time available to dissolve the underlying rocks. The ocean itself is conceptually divided into four sub-oceans, referred to as “northern”, “western”, “eastern” and “southern”. Currents running along the last three also mean that there is in a sense a further ocean not separated by land from the others. There are six continents. A relatively hospitable one is situated in the southern polar region, where the temperatures remain low enough for practically the whole surface to be lava-free. The corrosive atmosphere and high gravity, of course, remain. Most of the surface from the northern coasts of the polar continent is molten although the smallest continent, referred to as “Southern” is relatively free of precipitation. There are then two triangular continents, both linked to northern ones, referred to as “West Triangle” and “East Triangle” . The larger one, East Triangle, has two large areas free of precipitation but like Southern is extremely hot. West Triangle has a small stretch with practically no precipitation. Adjoining East Triangle is the Great Continent of the northern hemisphere. This is the largest continent of all, and its northeastern region is again cool enough not to kill someone quickly. The same is true of the final continent to be mentioned, the Lesser Northern Continent, although this and the Great Continent become very hot nearer the equator.
The surface of the planet is young. Unsurprisingly, the oceans are in constant motion, but the oxidane also eats away at the solid surface over a much longer time scale, although the occasional catastrophe can make major changes very quickly. WInds are another significant erosive factor. Also, in a process not found on our home world, the surface as a whole is constantly remodelled over a period of millions of years and the continents move around, collide with each other forming island chains and mountain ranges and split apart. This is, however, a very slow process. One consequence of this along with the erosion is the near-absence of impact craters.
A paradox of Sol III is how such a hot planet with a highly reactive atmosphere can remain in a fairly stable state rather than all the dioxygen reacting with the surface rocks and being removed from the atmosphere. The solution to this is quite remarkable: there are two balanced biochemical processes, one combining oxidane and gaseous carbon dioxide into energy-storage compounds with the aid of stellar radiation which releases the toxic gas as a waste produce, and another which combines the energy-storage compounds with dioxygen and releases carbon dioxide. Things were not ever thus. The planet went through a stage early in its history at an equable temperature, though still higher than our home world, with a harmless and hospitable atmosphere. Then, a certain group of microbes developed a mutation causing them to release the poisonous gas and the pollution of the atmosphere killed much of the biosphere. Hence not only is there life on the planet, in profusion in fact, but it actually requires the extreme high temperatures, molten lava and toxic atmosphere to survive. Although there are a few less extreme environments on the surface free of oxygen, all life on the planet uses molten oxidane to survive. Only a very few species could survive at temperatures we would consider comfortable or even survivable, and at such temperatures they’re in a dormant state from which they can only emerge in conditions of extreme heat. There is no true overlap between conditions life on Sol III would find tolerable and our own definition of survivable conditions.
Leaving microbes aside, some of which have biochemistry a little closer to our own with the proviso that they don’t employ ammonia, the larger organisms on the surface fall into three categories, which are covered below. It might be thought that the high gravity would make a buoyant environment more suitable for life, and in fact there is indeed more life living within the oxidane than out of it, there is also plenty of life outside these conditions. Although land life on Sol III tends to be smaller and stockier than the kind we’re familiar with, it’s as diverse and widespread as it is on our home world. One difference is that our own life originates from three different stocks due to our independent lake networks, whereas all life on Sol III is related because it originated in the ocean, or at least spent a long time evolving there before becoming able to leave it and exploit other niches.
One form of macroscopic life tends to use a prominent green pigment to absorb red light from the star to drive a nutrition-synthesising process. Its reliance on red light may reveal how life on Sol III is at a disadvantage compared to life on worlds near to redder stars. It’s this process, known as photosynthesis, which was responsible for poisoning the planet and causing the extinction of most life forms earlier in its history. Most large organisms reliant directly on photosynthesis do not move much of their own volition and the terrestrial varieties often bear colourful genitals which attract motile organisms to bear their semen to other members of their species and fertilise their eggs.
Another form of life tends to be able to move of its own accord and survives by consuming the bodies of other, often living, organisms. Their anatomy and physiology is usually centred around their need to move dissolved gases around their bodies, which they often manage using a system of tubes and one or more pumps. Their reliance on dioxygen and need to remove carbon dioxide gas from their tissues necessitates that all of their bodies need to be in close contact with a respiratory fluid, and all of the larger organisms also have entire body systems to deal with gases, either dissolved in the water around them or present in the air. In the case of the dominant class of animals, as they are known, on the land, this has limited their size as they rely on tubes open to the atmosphere. Incredible though it may seem, most animals can’t survive more than a few minutes without a constant supply of dioxygen.
The third form of life forms a kind of bridge between living and non-living parts of the food chain. Like the photosynthesisers, these are largely sessile and immobile, and tend to live off a substrate consisting of the dead or diseased bodies of other organisms. They do not photosynthesise. Many of them consist of subterranean mats of fibres which produce occasional fruiting bodies above ground level. Some of them are also parasitic. Without this group of organisms, there would be an ever-increasing unusable biomasse which would eventually cause all advanced life on Sol III to grind to a halt.
Animal evolution on Sol III went in a somewhat surprising direction. Unusually, a particular kind of fluid-living animal developed a hard internal skeleton and its descendents were able to use it to aid their movement rather than the more usual arrangement of holding them in place. These have proliferated into a variety of forms, though they constitute a small minority of species on the planet and animals themselves occupy much less biomasse than the plants (the photosynthesisers). Of all these species, one rather large, by the standards of the planet, type has become dominant over the planet through a technology based initially on the use and control of the runaway oxidative reaction and the discovery of language, which is acoustic and mediated by means of the organs which evolved to exchange gases. Remarkably, in spite of the intense gravitational field, these animals are able to achieve an erect bipedal gait.
It should be noted that the pace of animal life on Sol III tends to be very frenetic. This seems to be due to the high temperature and the employment of dioxygen as a means of releasing chemical energy. This hyperactivity doesn’t apply to plants to the same extent. It’s all the more so for those animals whose bodies rely on their own heat to drive their metabolism, and unsurprisingly this includes the technological species. Dormancy is a less significant phase of life for many animals living on the planet, partly because the years are shorter and in many parts of the world the seasons are less extreme. However, many species do become dormant on a diurnal basis for a considerable fraction of the planet’s rotation period, often when it faces away from the star, and depriving them of it for surprisingly short intervals leads to increasing mental derangement. The need of such organisms for food, oxidane and their respiratory gas is quite extreme compared to our own. This constitutes a barrier to space travel, as it means they are unlikely to be able to survive interstellar space voyages as easily as we can. This may not be a bad thing because there is a tendency for some members of the species to be quite violent, but this is also likely to be self-limiting. However, it’s probably better not to speculate too much about this aspect of their nature without more data.
One major lesson to learn from the complex life present on Sol III is that we may have restricted views on what constitutes an hospitable environment for the advent and evolution of advanced life forms. Before this discovery, the proposal that a sophisticated biosphere could exist on a planet two-thirds covered in molten rock with a dense caustic atmosphere capable of eating through metal, with a high gravitational field and temperatures far above boiling point over most of its surface, circling an ageing Sun much hotter and more massive than our own would have seemed ridiculous to all. These life forms can not only tolerate living with acidic molten rock in an aggressively reactive atmosphere but have evolved in tandem with it to the extent that depriving them of the gas for more than a few minutes is uniformly fatal and they need a continual intake of liquefied dihydrogen monoxide to survive more than a couple of rotations of their home world. Who knows what the inhabitants of Sol III might consider suitable conditions for life given their own extreme circumstances?
Any resemblance to Arthur C Clarke’s ‘Report On Planet Three’ is not entirely coincidental.
“Chauvinism” is quite an old-fashioned word for prejudice against a particular group. Nowadays each has its own word, generally consisting of the name of the type of group plus “-ism”. It comes from a Bonapartist soldier called Nicolas Chauvin, who insisted on maintaining his support for Napoleon after the Bourbon Restoration, and was then extended to apply to any type of fanatical devotion to or against a group or cause. In the light of the dangers posed by the use of the word “terrorism”, it might be worth bringing it out of retirement to refer to a particular kind of fanaticism which doesn’t currently have an obvious word to describe it, although “fanatic” is a less ostentatious option.
The use of “male chauvinist pig” apparently dates back to the 1930s CE. It has a rather old-fashioned tone to it now, but maybe it deserves reviving. For a start, it doesn’t lend itself to referring to sexism both ways, which is a contentious issue. It can only mean prejudice against women and girls. “Female chauvinism” is also used sometimes. A notable aspect of it is that it refers to the individual in the group to which there is a bias rather than a group, one member of which there’s a bias against. “Racism”, for example, refers to the category of race and not to a specific ethnicity, but very often refers to White racism against others, and this centring on the member of the group responsible for the prejudice is quite helpful conceptually. I don’t think “White chauvinism” is a common utterance, although there’s an interesting Communist pamphlet with that title dating from 1949, but it works quite well as a way of emphasising Whiteness and White fragility. However, the word has long since gone out of fashion in these uses.
A more specific use of the word “chauvinism” seems to have started with the well-known science populariser Carl Sagan in the late 1960s. He uses it to refer to biasses in ideas about extraterrestrial life. Examples would be “carbon chauvinism” and “water chauvinism”. The idea here is that a particular characteristic of life as we know it on this planet leads us to conclude that all life must have that characteristic, and this restricts the places and circumstances in which we might consider or look for other kinds of life. It might even affect how we view life on this planet because of the possibility of a “shadow biosphere”. It’s conceivable that even on, or perhaps in, Earth, there are other forms of life which don’t share our chirality or chemistry. For instance, the phenomenon of desert varnish, a dark coating which forms on rocks in arid areas, has been suggested as the action of undiscovered life forms which are not like the ones we know about, and a more outré suggestion is that silicon-based organisms live within this planet but never come anywhere near the surface. Carl Sagan, if I recall correctly, described himself as a carbon chauvinist but “not that much of a water chauvinist”. That is, he couldn’t conceive of a way biochemistry could emerge if it wasn’t based on carbon, although he did believe in the possibility of other elements substituting for some of our own. Here are a few entries from his Encyclopedia Galactica:
This one appears to have carbon, hydrogen and oxygen like us but lacks nitrogen, sulphur or phosphorus. It also utilises helium, which must be non-chemical. Germanium and beryllium also have no biological rôle on this planet, and it looks like this civilisation has no historical association with planets.
More details of the same explain further. They are not a single species but an alliance of some kind, perhaps symbiotic, and can apparently only survive in interstellar space because they depend on superconductivity, which only occurs at a low temperature.
This is us:
The last entry might be a bit depressing! This was in 1980.
I mention chauvinism now because I’ve had some difficulty wording my writing in this blog recently. There is an issue with the way we can refer to what I’m going to call “worlds” for argument’s sake in this paragraph. We tend to talk about planets as potential abodes for life, including technological cultures, but this is rather misleading. Considering our own Solar System, we have one body which is established to have had life on it for æons, our own Earth, but other worlds have been considered. At the moment the candidates seem to be: the upper atmosphere of Venus; the surface and oceans of Earth (quite a strong candidate that one!); Mars; the upper atmosphere of Jupiter; the interior oceans of Europa, Ganymede and Callisto; the surface and interior ocean of Titan; the interior ocean of Enceladus. There are a couple of weaker candidates in Ceres and Pluto. That gives us four planets, two dwarf planets and five moons. Hence even in our own system the possible places for life as we know it are mainly non-planetary, and constantly referring to “planets” in other star systems as places where life might evolve or appear without technological intervention starts to sound rather prejudiced. Maybe planets tend to be less suitable than other types of world.
The reason for most of these possibilities in our Solar System is that they have internal oceans. Europa and Enceladus in particular have rather suitable ones. Ganymede, Callisto and probably Titan also have liquid interiors but they’re more like Earth’s mantle than oceans, which might make them less friendly to life as the supply of other elements than hydrogen, oxygen and perhaps nitrogen might be very limited or non-existent. The geysers on Enceladus, on the other hand, do contain organic molecules with molecular weights above two hundred daltons, which is slightly larger than glucose, so the complexity may be considerable, and this is the only place off-Earth so far where such large molecules have been detected. Another very common finding, even in places where life is very unlikely, is tholins, which are reddish tarry organic substances present on many asteroids, centaurs, Titan, Europa, Rhea, Pluto and Ceres, although it isn’t clear that tholins are responsible for the red terrain on Pluto. Tholins are like the “cousins” of organic life forms, because they’re generated by the action of radiation such as cosmic rays on simple organic compounds. They’re bound to be common on small solid planetoids and comets throughout the Galaxy, and the question arises of whether we are the black sheep of the family in that we’re the rare exception, or whether life is just what happens instead of tholins in similarly widespread conditions.
It seems moons with sub-“terranean” oceans are a likely place for life to develop provided there’s an energy source and sufficiently varied elements, along with sufficiently low salinity. That last criterion may be surprisingly hard to satisfy. The total amount of liquid water in the Solar System is many times that found in our oceans, and the proportion of water on the moons involved is also much greater than that of the oceans to Earth. The energy source may be the Sun but is more likely to be tidal forces acting on the moon from surrounding large moons or the large planet it orbits, or it may be radioactivity as it is with our planet’s interior. If intelligent life arose in these conditions, it might be blind, unable to produce fire and unaware of anything beyond its ocean, since there would be a thick layer of ice above it. That said, it might also be tempted to drill a hole in that ice to see what’s outside or perhaps follow the course of a geyser or cryovolcano out into space, and it would be easier to leave most moons’ gravity wells than Earth’s, particularly as only Titan among these has a significant atmosphere, since they’re much smaller and less dense than this planet. It’s still possible that some kind of exothermic reaction could replace fire in their technology, but they might be stuck in the stone age if they exist at all.
I’ve already talked about exotic life in neutron and ordinary stars, which are of course not planets either, and there are also “rogue planets”, which wander through interstellar space too far from any stars to become associated with them. These will have been hurled out of star systems at some point, but life could possibly still arise on or in them if there is volcanism, or in any moons of the type mentioned if they’re tidally heated. In a sense these are actually proper planets, because the word planet means “wanderer”, which is what these do rather than orbit, which is what we tend to think of planets as doing. This actually means that etymologically these aren’t planets at all. Not only is Pluto not a planet, but nor is Mercury, Jupiter or Mars. In fact Pluto is in that sense more of a planet than the others because its orbit is more erratic and probably chaotic then theirs. However, it’s a fallacy to take the original meaning of a word as gospel and base one’s arguments on that, as can be seen with the idea that homophobia is misnamed because it’s hatred rather than fear. Maybe “heterosexual chauvinism” would be a better way to describe that combined with biphobia and panphobia.
There is also the question of what a technological species or perhaps intelligent machines would do if it got into space. In the mid-1970s, a plan for a rotary space colony about a mile in diameter (it was an American project, which might explain the units) situated at the L-5 gravitational equilibrium point between Earth and Cynthia was put together, and on this idea was built the expectation that if humans did move out into space, they might not actually be very interested in settling on, for example, Mars, when tailor-made orbital environments could be devised much more easily. It’s debatable whether such habitats are economically viable and the first would depend on the existence of industry on Cynthia to work, but there are different motives for going into space such as rescuing some, and that’s a very small fraction, of the species from a major asteroid strike or some other mass extinction-type disaster, and the motives of aliens would of course be unknown. Nonetheless it makes a lot of sense to bypass planets entirely and just build wheels in space, and beyond that perhaps Dyson spheres and ringworlds. Extending this far enough into the future, perhaps the most suitable places for habitation wouldn’t be found near Sun-like stars at all but the likes of blue supergiants like Rigel or the Pleiades rather than the likes of α Centauri or τ Ceti, because the former have very deep habitable zones and plentiful radiation. These are also the names that turn up in Golden Age science fiction because people have actually heard of these places. ETs might also board space arks, initially to get to nearby stars but take so long to get there that they no longer see the point of disembarking once they reach their destinations, and just carry on voyaging. There’s another answer to the Fermi Paradox: aliens leave their home worlds, establish colonies in space or launch spaceships to nowhere (leaving any place?) and their original abodes just go wild again. Also, we’re looking at the wrong stars for technosignatures.
There is one more really wild possibility: maybe life evolves in space and stays there. Life evolving in space isn’t a particularly new idea. Fred Hoyle and Chandra Wickramasinghe claimed in 1974 that the reddening of distant galaxies attributed to the expansion of space is in fact explained by microörganisms absorbing their light and they weren the first to claim that life here comes from elsewhere. More recently it has been noted that the whole of the early Universe had the right conditions for life, being fairly warm, dense and having all the right elements in close proximity to each other, for the kind of life we know about. Cosmic strings, of course, also existed by this point, so if that kind of life exists at all, it may have done so even before that happened. This is leaving out all the other possible kinds of life, such as plasma, and there have been thoughts about life based on liquid helium or superconductors, although I don’t know how that would work in detail. All of this is very vague.
To finish then, perhaps we think too much about planets when we consider alien life. It is in fact notable that we don’t seem to have a simple word to refer to heavenly bodies which are not stars in general. Maybe if we had a future, we would find ourselves eschewing both Earth and other planets just to live permanently in space and things here could go back to how they were before we evolved. They probably will anyway after we’re extinct. Meanwhile, maybe there are countless civilisations in the Universe trapped under heavy atmospheres or the bottoms of frozen over oceans in eternal darkness who don’t even know there is anything else, while out there between the stars are wraith-like beings thousands of kilometres across with their own societies, or living starships who evolved on their own. It has been said, after all, that the Universe is stranger than we can imagine.
Alchemist Hennig Brand looks focused, if maybe a bit drained, in this 1795 painting by Joseph Wright. The painting depicts Brand’s discovery of the chemical element phosphorus.
I have repeatedly, perhaps incessantly, referred to the Fermi Paradox on here, but one thing I have never done is to do a survey of the most often given explanations, plus a few less common ones, so I’m going to do that here.
Before I start, it’s probably worth stating clearly what the paradox is. It goes like this. There are thousands of millions of stars in this galaxy, and innumerable galaxies in the Universe, and many of those stars are suitable for life-bearing planets, yet we never seem to detect or encounter any intelligent aliens. Why is this?
Before I get going, I want to mention the Drake Equation. This is a surprisingly simple equation thought up by the space scientist Frank Drake in 1961 CE. It’s simply a series of factors, all unknown at the time, multiplied together. It looks like this:
To explain the variables and the unknown constant N then, N is the number of civilisations with which communication might be possible in this galaxy. This figure is arrived at by multiplying the following factors:
R* is the rate of star formation in this galaxy.
fp is the fraction of those stars with planets.
ne is the average number of planets which can support life per planetary system.
fl is the fraction of planets on which life appears at some point.
fi is the fraction on which intelligent life develops.
fc is the fraction of intelligent life which develops technology making it detectable from elsewhere in the galaxy.
L is the length of time detectable signs are there.
There is said to be a problem with this equation first of all, which is that it’s susceptible to chaotic influence. The Club Of Rome released a report called ‘Limits To Growth’ in 1972 which predicted that various mineral resources would run out very quickly, but this didn’t come about because at the time it wasn’t appreciated that the results of a mathematical model often depend very sensitively on the exact values of the variables involved, now known as the Butterfly Effect. It’s been suggested that the same issue appies to the Drake Equation, in that most of the variables are not even approximately known, let alone exactly. And there’s another problem, which I’m going to illustrate with something personal. I used to have a list in my head of the ideal partner, and there weren’t many criteria on it. It amounted to similar values, personality traits of particular kinds and common interests. A short list. I stopped taking this approach eventually because I decided it wasn’t ideal for a number of reasons, but I also noticed something quite odd. There was one person who was absolutely ideal in these respects, and was also unavailable, so I began to look elsewhere, and was surprised to find that after many more years there wasn’t even one other person who satisfied those criteria even remotely. Don’t worry about me, by the way – I took a different approach and it worked out fine. The same phenomenon afflicted the a particular army when it attempted to produce a small range of uniforms somewhat suitable for everyone. Given criteria such as arm and leg length, chest and hip circumference and the like, all quite important for the clothes to fit, they found that nobody at all had the same such dimensions, and it was impossible. I’ve mentioned this before of course. Applied to this equation, it’s easily conceivable that working through all the variables, if they were known, could result in N equalling one, namely us humans here on Earth, and that’s it. Some of them are much better known now, or at least fp is: there are a very large number of stars with planets, probably most of them in fact, and the ones which don’t have them would be unsuitable for life anyway because they’re short-lived and life doesn’t have long to develop on them anyway. There also seem to be examples of planetary systems in which multiple worlds are suitable for life, such as TRAPPIST-1, with at least three planets orbiting within the habitable zone. The wording of the Drake Equation is also somewhat inappropriate, as it fails to take into account that moons might also be suitable for life. These increase the value of neconsiderably. fp is effectively close to one, and ne is quite possibly quite high. For instance, in this solar system it could be as high as 8 if moons are included. The presence of life on, or rather in, moons is, incidentally, one possible answer to the Fermi Paradox.
Using the information available at the time, Isaac Asimov worked his way through the equation in his 1979 book ‘Extraterrestrial Civilizations’ and concluded that there were 530 000 such civilisations in the Milky Way. His approach was quite exacting. For instance, he excluded the nine-tenths of stars which are in the galactic core and assumed that the total length of civilisations per planet averaged at ten million years, but was shared between different intelligent species evolving on the same planet. On the other hand, the book was written before it was realised that the Sun would make this planet uninhabitable æons before it would start to become a red giant. I think Asimov’s approach was a little tongue-in-cheek, but there is an issue about whether once intelligence evolves, it will ever disappear again on a planet until it becomes uninhabitable. We may also be in a position where once evolution enters a certain state, the appearance of the kind of intelligence which leads to technology may occur repeatedly. It’s been noted that there are a number of other primate species which now use stone tools, for example, and the nature of intelligence among crows, parrots, elephants and dolphins as well as primates is quite like ours. Given that Asimov’s estimate is exactly correct, which is unlikely, this makes it possible to estimate the average distance between such civilisations. The volume of the Milky Way Galaxy has been estimated at eight billion (long scale) cubic light years. The central nucleus, according to Asimov and others, is unsuitable for life, so assuming that to be spherical, which it isn’t of course, that gives the rest of the Galaxy a volume of around six billion long scale cubic light years. If there are 530 000 civilizations in that volume, that makes one per eleven million cubic light years, so that would make the average distance between them roughly 224 light years with spurious accuracy.
I’m actually going to do headings this time!
Absent Aliens
The most straightforward, and in a way even the most scientific and sceptical explanation, is that Earth is the only place in the Universe with life on it. There are various versions of this, but the simplest is just that life arose on this planet by sheer luck, and is practically impossible. Nowhere else in the Universe is there so much as a bacterium. Since we only seem to have one example of life known to human science, this is the only explanation which doesn’t rely on conjecture. At first sight, it might seem unlikely that there’s no life anywhere else although strictly speaking life would only need to be rare for this to be the explanation. There is in fact a peculiar issue with the origin of life on this planet. Although taking a few simple compounds as would’ve been found in the primitive atmosphere and oceans and exposing them to ultraviolet light and electricity does produce many of the more complex chemicals found in living things, there is an important set of compounds which are completely absent. DNA and RNA are very complex of course, but are made up of fairly simple building blocks of ringed nitrogen-containing compounds called purines and pyrimidines which comprise the rungs of the ladder and encode the genetic information. As far as I know, such compounds have never arisen in laboratory conditions. Clearly living systems can all synthesise them or they wouldn’t exist, but this happens through complex enzymes and already-organised biochemical pathways which rely on genes, made of those very same compounds. It’s a chicken and egg situation, and perhaps this means that the appearance of purines and pyrimidines is the single unlikely missing link on the way to life which has arisen just once in the entire history of the Universe, and therefore that the only place in the Universe where there is life is this planet. However, even if this is a one-off event, it doesn’t necessarily entail that life is found only here because it may still be that it arose somewhere in the Universe and spread widely. A few million years after the Big Bang, the whole Universe was much smaller, denser and warmer, to the extent that all of it was between the freezing and and boiling points of water and matter was dense enough to support life as we know it in space, and the elements from which it’s made were already available. Hence it’s possible that life has been around for almost as long as the Universe, and that it has a common origin, being able to spread as the Universe expanded.
There are even hints that life is present elsewhere in this Solar System. Some people, myself included, interpret the 1976 Viking missions’ ‘Labeled Release Experiment’ as positive in detecting life. This involved taking a sample of Martian soil (I always find it strange when extraterrestrial materials are described as soil. Martian soil is more like a mixture of rusty talcum powder and bleach), exposing it to a radioactively labelled soup of nutrients in water and measuring any carbon dioxide given off for radioactivity. It assumed that water would not be harmful to any organisms living in the soil. Anyway, the experiment was positive, but cast in doubt in view of the fact that the other two were negative. On Venus there have been three separate pieces of evidence for life in the upper atmosphere, not just the claim of phosphine. There is also something in some clouds which absorbs ultraviolet light and a compound called carbonyl sulphide is produced which is difficult to account for in the absence of life. On one of the several moons in the outer Solar System with subterranean water oceans, Saturn’s Enceladus also has geysers in which biochemical compounds have been detected. Other candidates include Titan, Europa, Ganymede and Callisto, and perhaps Jupiter. However, I don’t think this is good evidence for life elsewhere in the Universe. I think it could easily turn out that if there is life in these places, it has spread out from a common origin somewhere in this Solar System and without good data from elsewhere in the Galaxy we might still be alone apart from that.
One argument for life being common is that it began so very early on this planet, very soon after it first formed in fact, which makes it seem almost inevitable given the right conditions. Alternatively, it may have infected this planet from elsewhere, possibly Mars. However, this doesn’t follow because we only have one example of life known to us. There is also a very specific reason why life might be rare or non-existent elsewhere: phosphorus.
Back in the day, Isaac Asimov (yes, him again!) scared the living bejesus out of me in his article ‘Life’s Bottleneck’, highlighting a peculiar and largely ignored major environmental problem. There are all sorts of chemical elements needed for human life of course, but the major ones for all life make a short list: carbon, oxygen, hydrogen, nitrogen, sulphur and phosphorus. Phosphorus is far less abundant than the others and living things are distinctive in that they concentrate phosphorus way more strongly than the other elements compared to their surroundings, on the whole. The way industrial societies tend to deal with human excretion is often through sewers which expel the treated waste into the water and ultimately the sea. This waste is of course quite high in all sorts of elements, but is also sufficiently high in phosphorus that the alchemist Henning Brandt was able to discover it in the seventeenth century from performing transformations on human urine, as in the picture opening this post. The phosphorus which enters the sea only returns to the land very slowly because it’s mainly recycled by continental drift and gets washed off the land by rain anyway. Humankind began to notice in the early nineteenth century that the limiting factor in food production was phosphorus, and proceeded to mine phosphate rock for fertiliser, which has liberated a lot of phosphorus into the environment and leads to algal blooms and the like, which tends to poison the oceans and deprive aquatic environments of oxygen due to increased biochemical oxygen demand. It’s hard to know exactly what anyone can do about this which would make much difference, but a few steps which could be taken are to increase the amount of food from marine sources in one’s diet, which doesn’t mean fish, crustacea and the like because of their unsustainable “mining” but seaweed, and change the way one gets rid of urine, fæces being more a public health hazard which would probably be best dealt with by sanitation services, which does however need to happen, so that is a lobbying and pressure group-type issue. Anthropogenic climate change is of course vastly important, but it’s only one of various vastly important environmental issues, and the phosphorus one in particular is disturbingly ignored. Things are far from fine in that area.
Phosphorus limits biomasse. It’s the limiting factor in it to a greater extent than other elements because they are far more abundant. It might not be going too far to call the kind of life we are “carbon-phosphorus-based” rather than “carbon-based”, because the element has two completely separate but vital rôles in all life as we know it. One of these is that it stores energy and provides a chain for its release from glucose, even in anærobic respiration, in the form of adenosine triphosphate (ATP). This is how the Krebs cycle links with the rest of metabolism. Without ATP, there is simply no life. The other is that it forms the sides of the DNA and RNA molecules along with a sugar, in the form of phosphate. Again, without nucleic acids, there is no life, which harks back to the difficulty in finding a feasible process for purine and pyrimidine synthesis. The discovery that phosphorus was a major limiting factor in biomasse may not simply apply to life on this planet, but throughout the Universe.
Why is this an issue? Wouldn’t we find that other planets in the Universe have about the same amount of phosphorus as there is on Earth or in this Solar System? Well, no, or rather, quite possibly not. Odd-numbered elements are usually rarer than their even numbered neighbours in the periodic table, and phosphorus is element number fifteen. Of the other elements playing a major rôle in life here on Earth, only nitrogen and hydrogen have odd numbers. Hydrogen is a special case because it’s the “default” element. In parallel universes whose strong force is slightly weaker, the only element is hydrogen. Its abundance there is one hundred percent, and most atomic matter in the Universe is in fact hydrogen, because the rule doesn’t apply to it. It’s a given. Nitrogen is still the seventh most abundant element because it’s fairly light and therefore likely to form. Phosphorus is the seventeenth most common everywhere on average, and is only formed when silicon atoms capture neutrons and decay. Only 1‰ of Earth’s crust is phosphorus and 0.007‰ of the matter in this Solar System. Its main mode of formation is in Type II supernovæ.
Supernova 1987A, a Type II supernova in the Large Magellanic Cloud
Type II supernovæ result from the collapse of stars whose mass is between eight and four dozen times the Sun’s. They only “burn” silicon for a very short period of time, during which a few silicon atoms will become phosphorus. Then they explode, scattering their elements across their region of the Galaxy in a shockwave. As time goes by, these supernovæ slowly increase the abundance of various elements, including phosphorus, but the regions of the Galaxy where the element is relatively abundant may be quite small and scattered, at least for now. This means that effectively the Universe, and on a smaller scale our galaxy, may be a phosphorus desert with a few small oases where it is even remotely “abundant”. Asimov said of phosphorus that we can get along without wood by using plastic, without fossil fuels by using nuclear power and without meat by substituting yeast, but because phosphorus is such a fundamental part of our metabolism there is no such substitute.
Now the question might arise of why so much importance is placed on phosphorus here when life seems to be so very adaptable and able to find ways round problems, and this is indeed so, but there are reasons for believing that this cannot happen with this element. It’s locally more abundant in geothermal vents and carbonate-rich lakes, which have fifty thousand times as much oxygen as seawater has, and it can also become concentrated in rockpools due to capturing the runoff from water and concentrating it when it evaporates at low tide, so there are various high-phosphorus places on this planet where life could have begun, which may well not be elsewhere in the Galaxy. Now suppose there are various different processes which could lead to life beginning here which do not involve phosphorus, which seems feasible and in fact it’s considered slightly odd that all life known here seems to have a common origin. The one which needs phosphorus is at a disadvantage compared to the ones which don’t, because it relies on a scarce element and wouldn’t be able to spread so easily to environments where other life for which it was not a limiting factor would be able to thrive. Therefore it very much looks that the kind of life which exists on this planet has the only kind of biochemistry possible here.
This could have major consequences for our own space travel. It might mean, for example, that we can’t settle on planets in distant star systems and thrive without bringing our own massive supply of phosphorus, and this also makes it more difficult for other intelligent carbon-based life forms to colonise the Galaxy, because not only are there vast distances between the stars, as we already know all too well, but even those distances are small compared to the small spheres of phosphorus-rich systems scattered sparsely through the Milky Way. They could be thousands of light years apart. Moreover, although the Universe is very old, it may have taken this long to accumulate enough of the stuff for life to be possible at all, meaning that the idea of elder civilisations out there which appeared æons ago may be completely wrong. This leads to a second variant on the idea that life is rare.
We’re The First
It may be that we don’t know of any aliens because there aren’t any, but there will be one day, either because of us or because they will evolve later. The phosphorus bottleneck is one explanation for this, but it could also be that we got very lucky with evolution. Over most of the time this planet has existed, it’s had life all right, but it was single-celled and those cells weren’t even the more complex ones like amœbæ, and life chugged along just fine, though it didnæ end up producing anything very impressive-looking or even visible to the naked eye. It could very well, for all we know, have continued in that vein until the Sun roasted it out of existence, but it didn’t. In fact this is another explanation entirely which is worth exploring as such: simple life is common, complex life rare.
One way to look at evolution as it’s happened here is as a series of improbable events. Some even say that the advent of oxidative phosphorylation is improbable, and that even anærobic respiration was an improbable step, which would limit life so severely as to effectively rule it out in any meaningful sense. Beyond this, the evolution of cells with separate nuclei containing DNA surrounded by an envelope of cytoplasm with symbiotic bacteria living within it also seems quite unlikely, and we haven’t even got to the simplest animals and plants yet. Maybe on other planets these improbable events have taken longer than they have here, or don’t happen at all, and although there will be intelligent life there one day, that point is hundreds of æons in the future. There are a couple of unexpected things about the Sun. One is that it’s a yellow dwarf rather than a red dwarf, and since those are both apparently suitable for life-bearing planets and liable to last many times longer than the Sun, a random selection of intelligent life in the Universe might be expected to result in finding an organism living on a planet circling a red dwarf 200 000 000 000 years in the future. The other weird thing about the Sun is related to this. If there is something ruling out life on red dwarf planets, such as frequent flares, it’s still more likely that intelligent life would evolve on a planet slightly cooler than the Sun, that is an orange dwarf such as α Centauri B or either of the 61 Cygni binary system, because the star would both last longer as such and have a habitable zone which lasted longer in the same place. Perhaps the reason the Sun is a yellow dwarf is that we are ourselves unusual and have evolved unusually early, so the absence of aliens is in a way connected to the unusualness and apparent unsuitability of this star.
The ‘Red Dwarf’ universe has the second version of absent aliens which in fact amounts to “we’re the first”. There are other intelligences in ‘Red Dwarf’ but they’re all derived from Earth in one way or another, and this is “word of God” because Rob Grant and Doug Naylor have said so themselves. In this version of us being first, we are indeed the first but will go on to seed the Universe with our machines and organisms until it teems with intelligent life. We just happen to be living before that’s happened. I would argue against this for the same reasons as I did here: if that’s the case, aren’t we just incredibly unlucky to have been born before it happened? My answer to this is that it will never happen, but there’s a further probabilistic difficulty in the fact of our existence here and now on this planet 13.8 æons after the Big Bang: the scepticism about our future is about time, but could equally well be applied to space. If I am a random intelligent entity in the Universe and it’s normal for intelligent life forms to expand out and settle the Universe in untold high population numbers, why am I not one of their much greater number? Here’s a possible answer:
Intelligent Life Destroys Itself
This was a popular idea from 2016, when Donald Trump got elected, but has been stated many times, in connection with climate change, the Cold War and hostile nanotech. Maybe there’s something about monkeying around with the world which ends up killing species off. This could be quite low-key. For instance, it’s possible that if we had continued with a mediæval level of technology and population and it had spread around the world, although climate change might not be as severe as a result of our own activities, we might still reduce the fertility of the soil and have plagues and famines wipe us all out in the long run. However, once an industrial revolution has occurred, bigger problems start to emerge, the most prominent and obvious being anthropogenic climate change in our case, but another issue is the use of weapons of mass destruction, or AI, complexity or nanotechnology causing our extinction. The Carrington Event is a famous solar flare in the mid-nineteenth century which led to electrocutions from the only electrical telecoms which existed at the time, telegraphy. If this happened now, and it is likely to recur quite soon statistically, the internet and devices connected to it could be physically destroyed, and we are now very dependent on it. Nanotechnology is another potential threat, with the “grey goo scenario”, where tiny machines reproduce themselves and end up eating up the entire planet. This has been explored and seems to be impossible, because limiting factors like phosphorus for life also exist for such machines in the form of other elements, but one thing which could happen with nanotech which is much cruder is that it simply becomes a ubiquitous particulate hazard for everyone. Complexity probably amounts to unforeseeable apocalyptic scenarios. For instance, climate change could lead to wars over water which would restrict access to metals needed to maintain a physical infrastructure we need to provide food. In a way, as an explanation of the Fermi Paradox the absence of aliens might constitute an important lesson for us, but the details are less important than the consequences, which are that there are no spacefaring or communicating aliens because they always die out soon after becoming capable to doing anything like that.
I actually do think this explanation has some factual basis, although it isn’t quite as drastic as it seems. I think there is a brutal pruning process in technological and social progress which prevents harmful aliens from leaving their star systems, and unfortunately in that process there are myriads of innocent deaths and enormous sufferings, holocausts and the like. The way I think it works is that tool-using species may either smoothly develop in a consistently altruistic way or in a more internally aggressive manner which may or may not be resolved by the time they attain the ability to travel through space. We are now at such a crucial stage, and we may destroy ourselves, solve our social problems and opt not to go into space or solve our social problems and expand into space. There may be a law of nature which means an overtly belligerent attitude is self-defeating and such species, although they may not be essentially aggressive, always destroy themselves rather than travel to other star systems. In other words, I believe in this explanation, but it may not be an explanation of the Fermi Paradox. I think it means that any aliens we encounter who have left their own star systems will automatically be peaceful and coöperative. If this is too tall an order then nope, there are no interstellar civilisations, although there may be aliens who haven’t wiped themselves out yet, and even aliens who occupy an entire star system. This is the opposite answer to the Fermi Paradox to the next, fairly recently devised, one:
The Dark Forest
This is named after the work in which it was apparently first suggested, 黑暗森林, by the Chinese SF writer 刘慈欣, Liu Cixin, in the ‘noughties, although it’s hinted at in the preceding novel, 三体, whose English title is ‘The Three-Body Problem’. Avoiding spoilers, the basic idea is that we never hear from aliens not because there are none, but because they’re hiding from each other. I’ve mentioned this before but it bears repeating here. Aliens are assumed to see each other universally as potential threats and will therefore act to destroy each other whenever they become aware of their existence. In response to this, they all hide themselves and the reason we detect no signals from them is that they assiduously avoid making themselves detectable. Against this dark background, humans are recklessly advertising our presence to all and sundry, positively inviting ETs to come along and destroy us, even if only to avoid attention being unwantedly attracted to themselves by even more powerful minds which would swat them like flies.
It can be argued that this situation reflects the real situation we observe in ecology, where camouflage and mimicry protect organisms from each other and disguises of various kinds are adopted to prevent themselves from being sensed, killed and eaten. I think 刘慈欣 has a rational approach to the issue, and in fact quite a positive message as he believes that we’ve got the idea of humans and aliens the wrong way round. He believes that there is a prevailing view that aliens will be friendly while we are aware of the hostility prevailing between powers in the human world, but that the real situation is that human beings are potentially much more altruistic than we give ourselves credit for, and it’s likely to be the aliens who behave in a vicious manner towards us. Other believers in the Dark Forest answer say that non-believers in it are being anthropomorphic by imagining that aliens would not be hostile, because the biosphere we know of is quite savage. I’d say that this is a projection, and also that to extend the comparison, there are circumstances where organisms positively advertise their presence, for example to seek a mate or as warning colouration. The former is a little hard to fit into this scenario, but the closest analogy would probably be something like exchange of information for the benefit of both cultures, a relationship described ecologically as symbiosis. For instance, assuming the presence of multiple hostile civilisations in the Galaxy, it would seem to make sense for two less powerful cultures to tell each other about the threats. Something like warning colouration is another possibility. A species of aliens might wish to broadcast its potential hazardousness to others in order that it not be bothered, rather like the Mutually Assured Destruction (MAD) scenario, and in fact the Dark Forest is based on game theory, which is influenced by MAD.
The idea of more powerful civilisations disrupting and destroying less powerful ones has a persuasive-seeming precedent in human history, because in general European and European-derived cultures have tended to do that to a horrifying degree on our own planet to other human cultures. This,though, is based on what happens within our own species in highly specific circumstances which rely substantially on the idea of territory and land use, along with a religious and political outlook used to justify those atrocities. It’s this which seems anthropomorphic to me. The Dark Forest seems to be the same situation translated into interstellar space and assumes that the species or entities involved are similar to us in the mode we have employed during history, which is likely to be highly atypical even for us, and we may also be projecting our own assumptions onto ecology when we assert these things. There are plenty of examples of peaceful coöperation between species, such as symbiosis and the very fact that multicellular organisms are themselves alliances of unicellular ones for mutual benefit in the same way as an ant colony is. There’s also the consideration that life on this planet has been around for a very long time now and it would seem to make more sense to nip things in the bud before intelligence of our kind has even evolved, but this hasn’t happened. However, I do maintain a modicum of sympathy and interest in 刘慈欣的 argument because I suspect it’s linked to dialectical materialism, and in order to assess it properly I would have to know more about Maoism, the current status of the Chinese 共产主义, his status with respect to the Chinese government and so forth. I would maintain that China, because it has a stock market, is capitlist, but that doesn’t mean it doesn’t have valid philosophical views built upon its ideology. It’s all a bit complicated, and interestingly something he goes into himself in his novels. Although I don’t agree with the Dark Forest at all, laying it out as a Marxist-influenced argument is interesting and may suggest other solutions to the Fermi Paradox which are freer from the taint of capitalism.
Spending Too Much Time On The Internet
I have felt since the early 1980s that there may be a trade-off between Information Technology and human space exploration. I don’t want to go into too much depth here but I suspect there is an inverse relationship between the two, such that the more IT advances, the less effort is expended on sending people into space and the more human beings explore the Universe, the less happens in the sphere of computing and the like. This is a subject for at least an entire post, and I won’t do more than mention it in passing here. Suffice it to say that when the Drake Equation and Fermi Paradox were first thought of, IT was very primitive compared to how it is now, although the internet itself is quite possibly the most predictable thing which has ever happened (see for example Asimov’s ‘Anniversary’ published in 1959 or Old Burkster’s Almanac in the 1970 ‘Tomorrow’s World’ book, which actually predicted the exact year it would take off (1996), so the link could’ve been made then. In fact, Olaf Stapledon predicted something similar in ‘Star Maker’ in 1937, where he imagined a species of aliens which ended up never leaving their home planet, which is doomed due to losing its atmosphere, because they end up lying in bed all day hooked up to a global information communications system, which also tellingly begins by encouraging cosmopolitanism but soon degenerates into echo chambers.
The “spending too much time on the internet” solution to the Fermi Paradox goes like this. We went through the Space Age and appear to have come out the other side. On this other side, we have an almost universally accessible network of devices for information and communication. If we are able to develop sufficiently convincing virtual worlds, we might all end up in the Matrix and not bother going into space at all. Perhaps this is what always happens to sufficiently advanced technological civilisations. The author of the Dilbert cartoons, Scott Adams, once stated that if anyone ever managed to invent the Holodeck, it would end up being the last thing ever invented because everyone would just end up living in that virtual world and not bothering with anything else. This is different to the idea of the Universe being a simulation because in this situation everyone knows where they are is not “real”, although Gen-Z-ers might argue with a definition of reality which divides meatspace from cyberspace with considerable justification, and willingly participates anyway. If you’re doing that, why bother to explore strange new worlds or seek out new life and civilizations. In fact you could do that anyway because I’m sure a virtual Enterprise would be one of the first things to be created in this virtual world, if it hasn’t been already. It wouldn’t be “real” in the way we understand it, but who are we to say? It would, however, mean we aren’t going to meet any aliens because they’re all on Facebook or something, which we may already have noticed is so.
One problem with this answer is that it assumes aliens are all similar enough that they get to a stage when they not only start to create communal online environments but also then get addicted to them and abandon space exploration. It isn’t clear that they’re similar enough even to have the same mathematics as we have, so why assume this is what happens? It may well happen to humans, but that could have little bearing on what happens anywhere else.
This can be turned round:
The Planetarium Hypothesis
There are several different versions of this and it blends into another version. The most extreme and probably easiest to state version is that we are living in a simulation, which Elon Musk claims playfully and perhaps not very seriously to believe. The argument that this is so in his case is based on the expectation that technological intelligences would very commonly get to the point where they could simulate the Universe, and within those simulations, more technological intelligences would do the same and so on, meaning that the number of virtual worlds compared to the real one is very large and therefore that we are much more likely to be living in one of those than the unadulterated physical Universe. Hence this is not the real world, and for simplicity’s sake, or perhaps as an experiment, we’re sitting in a simulation which, unlike base reality, is devoid of aliens. The alternative, according to Musk, is that in the near future we’re likely to become extinct, because there would then be no intelligent civilisations capable of simulating the Universe and therefore that we are living in base reality, but not for very long because there is about to be a massive calamity which will wipe us all out. I don’t find this argument to be at all satisfactory. Like the previous argument, it assumes that history will proceed in the same manner for everyone and that we all end up producing simulations. It also assumes simulations are possible when there are at least two good reasons for supposing they aren’t. One of these is the three-body problem. Three bodies whose attraction to each other is significant will behave chaotically in almost all cases and there are no ways of predicting their movement with a finite number of mathematical operations. There are exceptions to this. A few entirely predictable stable situations exist, most of which are too rare to occur in the observable Universe although there is one which may well exist somewhere in a star system in a galaxy far away. However, that’s the three-body problem. The Universe we experience has many more bodies than that in it. The number octillion has been mentioned in connection with this. For the Universe as we know it to be simulated, even the bits we’ve visited with space probes, an infinitely complex computer would be needed. Another problem is that of consciousness. Simulating consciousness doesn’t seem to be the same thing as actually being conscious, yet we know ourselves to be conscious. We could be mistaken about our substrate – maybe it’s transistors or qubits rather than brain cells – but for that to be so, panpsychism also has to be true, which as far as I’m concerned is fine but most people don’t accept that view of the nature of consciousness. There may be a functionalist solution though. A further objection is based on Musk’s own thought about the multiplicity of simulations. If a powerful computer can run a simulation of the Universe in which other computers can also run simulations of the Universe and so on, the largest number of simulations running would also be the most rubbish ones, at the bottom of the pile, because that’s the point at which the “tree” has its final twigs, and that means we’re more likely to be in a rubbish simulation, but we aren’t, and that simulation would also be too simple to allow any further simulations to be run. Minecraft exists, therefore we are not living in a simulation!
One point in favour of the Planetarium Hypothesis is that it’s highly sceptical and makes very few assumptions compared to some other solutions, and in that respect it’s similar to Absent Aliens. There are also less extreme versions of this which take the word “planetarium” almost literally. We have never bodily travelled more than 234 kilometres into trans lunar space, which happened with the ill-fated command module of the Apollo XIII mission in 1970. Therefore, for all we know the rest of the Universe could be faked for our benefit, although this assumes that the likes of the Pioneer and Voyager probes are just sitting somewhere being fed loads of false data or something. There’s a decision to be made in this explanation as to where one cuts things off and decides everything else is fabricated, and it begins inside one’s own head. This thought has been used at least twice by major SF writers. In the 1950s, Asimov (again!) wrote a story where the first astronauts to go behind Cynthia (“the Moon”) found it was painted on a board and propped up by wooden struts. Later on, Larry Niven, who had written himself into a bit of a corner with his Known Space series because he had to try to maintain continuity, playfully came up with the idea that none of it had happened and it was just being simulated in VR on Cynthia.
It’s been suggested that the almost perfect match between the apparent size of Cynthia and that of the Sun is a kind of Easter Egg, that is, a clue that we’re living in a simulation. It doesn’t seem necessary for the existence of intelligent life here that that match should be so perfect, and there seems to be no explanation for it other than chance. And it is peculiar. It will only hold true for the approximate period during which oxygen-breathing terrestrial animals can thrive here because the distance between Cynthia and Earth is increasing by a few centimetres every year. It would be interesting to run the figures about this, to see for example how big and/or distant a moon would have to be if we were orbiting within the habitable zone of 61 Cygni B or something, because there might be a clue there.
I have to admit it’s tempting to believe that the empyrean, as it were, is hidden from us by some kind of holographic Dyson sphere, i.e. that the planetary Solar System and Kuiper Belt are surrounded by a fake display of the rest of the Universe, just because it’s an appealing idea, and there are even reasons for supposing this to be the case. However, that would mean that Pioneers 10 and 11 along with Voyagers 1 and 2 either hadn’t hit the solid sphere of the sky, as it were, yet, or that they had but are themselves in a simulation of interstellar space. It was recently suggested that the Solar System may be enclosed in a vast magnetic tunnel as it moves around the Galaxy, but it seems to be several hundred light years wide and a thousand light years long, so if that’s the edge of the simulation it seems a bit pointless. Another appealing idea associated with this is that all that stuff about Venus being a hot, steamy jungle planet and Mars having canals and Martians living on it could be entirely true and we’re just having all that concealed from us and, again, fake data being fed to space probes. Of course, if human astronauts actually did go out there this would be harder to maintain, unless one begins to suppose that they’re all abducted and brainwashed or something.
The answer this kind of blends into is the
Zoo Hypothesis
This used to be my favourite answer when I was younger, and I just basically assumed it was true, but it lacks the parsimony of absent aliens or the Planetarium Hypothesis. If you’re familiar with ‘Star Trek’, you’re probably aware of the Prime Directive, also known as Starfleet General Order 1:
“No starship may interfere with the normal development of any alien life or society.“
We don’t know how extensive or organised any technologically advanced species or other intelligence which might exist outside our Solar System is, or anything about their ethics or politics. However, the admittedly anthropomorphic analogy with how things are here with uncontacted people on our planet, we do have at least a rudimentary ethic to protect them. We note that they are self-sufficient, unfamiliar with how things work in global society, highly vulnerable and at risk of extinction. Often the reason their lives do end up disrupted is due to governments or multinationals wanting to get hold of resources which happen to be located where they are. This is never going to be the case for Earth in terms of mineral resources, as even phosphorus is found elsewhere in sufficient quantities, if that turns out to be important, and there isn’t going to be any kind of invasion to get hold of metals or whatever from here. What we may have is culture and biodiversity. Speaking of biodiversity, there are reserves and national parks in many countries on this planet, so maybe we’re in one of those. It isn’t clear whether to an alien we would be more like an uncontacted indigenous culture or endangered wildlife, depending on how different our intelligence and minds are, but there are measures in place here for the protection of both. Moreover, when the difference is large enough, it’s possible for human technology to maintain an environment in captivity which may create a persistent illusion of the habitat an animal is found in before human interference, and we could be in such an environment.
I’m going to present my train of thought, as was, on this issue, starting with the premises of the Fermi Paradox. The Galaxy is more than twice as old as this Solar System, so it’s fair to assume that intelligent life evolved many æons ago, even before the Sun formed. This is also more than ample time for the Milky Way to become thoroughly known to the technological cultures that exist within it, and it can also be assumed that any species able to leave its star system must have achieved some kind of utopia in order to be able to use the energy and resources efficiently enough to do so. Therefore the probable situation across the Galaxy is that a peaceful and benign community exists which will protect the less advanced civilisations found within it. This applies to Earth. We are observed by aliens and there is a non-interference ethic which prevents us from being contacted because of the disruption that has been seen or modelled to occur in the past if it happens too early in the history of a species. This policy has been in place for thousands of millions of years. When we reach a certain stage in technological and perhaps social development (I actually think these always occur hand in hand), we will be contacted and, perhaps after a probationary period, invited to join the “Galactic Club”. There is well-worn standard procedure for doing this. It can also be supposed that because this society is so ancient and long-established that it works as perfectly as any society could, so the procedures can no longer be improved upon. I should probably also mention that back then, as now, I thought in terms of technological cultures rather than species. Individual races come and go in this scenario just like individual humans in society, but the culture is permanent, or at least very durable. This is the condition of the Galaxy.
Although my use of the word “culture” calls Iain M Banks’s fiction to mind, I began to use it before they were first published. The word is just very apt to describe this kind of situation. I used to be very confident that this was how things were, and it is more or less the Zoo Hypothesis. Where it falls down, I think, is in having a quasi-religious tone to it. It could be argued that this is akin to our own ancient tendency to project our wishes and stories onto the sky, and I do think this is significant. However, there are different ways to respond to that thought. One is that we unconsciously know how things are and therefore made various attempts to express that fact given the current state of knowledge throughout our history. Alternatively, the reverse could be true: we have a tendency towards magical thinking which results in religion, and this leads us towards imagining how to have things this way in the face of what we perceive to be powerful evidence against the supernatural. Some fundamentalist Christians accept the existence of aliens but see them as demonic. It’s very difficult to examine oneself closely and neutrally enough to come to a firm conclusion as to what belief in the Zoo Hypothesis is motivated by, and therefore to assess it scientifically or rationally. There are certainly inductive inferences operating within the argument, but perhaps not deductive ones. “Accusing” it of having a religion-like flavour is not the same as refuting it, and part of the decision as to whether to accept or reject it relates to how one feels generally about religion.
That said, there are some ways of arguing rationally against it. It only takes one small group within the Galaxy, perhaps the closer star systems in this case, to behave differently for First Contact to occur. Since I’ve concluded also that mature interstellar cultures must be anarchist, there would be no law enforcers to prevent this from happening. However, anarchist societies are not necessarily chaotic and may have customs which prevent such things from happening. For instance, queues are not generally legally enforceable but people rarely jump them due to social disapproval or the simple act of people providing the service one is queueing for ignoring violators, and there are apparently places where there are no laws regarding traffic priority at junctions, but people behave harmoniously according to custom. It hasn’t escaped my attention that I’m talking about Douglas Adams’s “teasers” here. As far as we can tell, though, this hasn’t happened. Or has it?
UFOs Are Alien Spacecraft
Like most people, I reject this out of hand but there’s a point to stating in detail examples of what people who believe this generally think. There is some variation in the details, but I think it works roughly as follows.
For quite some time now, perhaps since prehistory, this planet has been regularly visited by spacecraft ultimately originating outside this Solar System, containing intelligent aliens. These aliens sometimes abduct humans and other animals to do experiments on them. The governments of the world are aware of the situation but keep it secret from the public to avoid panic or because they’ve made some kind of deal with the aliens.
This view has a number of variants and is the basis of several religions. One such view is that ancient astronauts are responsible for world religions and have interfered in our history, perhaps even interbreeding with our ancestors or genetically engineering them for the appropriate kind of intelligence. Incidentally, this is known as “uplift”. Another view, of course, is that the human world is run by alien reptilian humanoids or shapeshifters for their own nefarious purposes and not for human benefit. There are also notions such as aliens wanting to get elements or substances from this planet which are rare elsewhere in the Universe, such as human enzymes or for some reason gold.
I stopped believing that UFOs were alien spacecraft when I was about ten, I think. There are a number of very good reasons to suppose this is not the case. The initial trigger that ended my belief was that the occupants of the craft were said to be humanoid in possibly all cases, which I saw as completely incompatible with them being aliens. For a while, I believed they were time machines and the beings on board were highly evolved humans from the future. Although I no longer believe this either, I still think it’s more plausible than the alien idea. I had a bit of a blip in my disbelief when I heard about the star chart aboard the spacecraft in the Hills’ abduction, which closely maps nearby star systems from a certain angle, but now think that this could be made to conform to the pattern drawn by projecting the stars in various different ways until a rough fit was achieved, which is in fact what happened with this.
There are various problems with the flying saucer hypothesis. One is the fact that people report humanoid occupants, although there are possible explanations for this. The entities could be manufactured or genetically engineered to look like us or convergent evolution might ensure that tool-using species are humanoid. Another is more serious: UFOs are visible. People report detecting them in various ways, such as on RADAR screens or more often visually. Even with our own relatively limited technology, we are able to make things almost invisible and undetectable on RADAR, but we are expected to believe that aliens can’t do this even though they can cross interstellar distances with ease. The alternative is that they want to be seen, but this is an unsustainable intermediate position because it doesn’t make sense for just a few craft to be seen occasionally. It can be confidently asserted that if they wanted to be invisible, they would be, so it then becomes necessary to explain why they don’t want to be. It’s fine as such if they don’t, but it would also mean the idea that they only associate with the “leaders” of the human race goes by the by. Also, the very idea that they would respect governmental power structures makes no sense. There’s no reason to suppose aliens would have government or that they would pay more attention to the people who happen to think they’re at the top of the pyramid. Of course, I’m personally convinced that they’re all anarchist, but there are other circumstances in which aliens might wish to subvert the hierarchy or just end up doing it anyway. Apart from anything else, they are after all aliens. They may not have the capacity to understand the nuances of human governmental systems, or they may arrive here not having learnt how it works. Or, they may wish to disrupt human society for nefarious purposes by inducing the panic world governments are supposèdly trying to avoid by keeping them secret. The nub is that if aliens were visiting us, they’d be able to hide from everyone, and if they didn’t hide from everyone they’d hide from no-one.
I do believe in UFOs of course. There very clearly are aerial objects which remain unidentified by any human observer. These are often things like Venus, birds, drones, weather balloons and so on, but I do also think there is another, very small set of other objects. These are secret military aircraft which happen to get spotted by people from time to time but whose existence isn’t openly admitted by the authorities. The one time I saw a UFO I couldn’t explain, that’s what it turned out to be, so maybe I’m biassed because of that.
I also believe that aliens would be benevolent for the reasons I set out under the Zoo Hypothesis.
Simply not believing that UFOs are alien spacecraft is not the same as believing we aren’t being visited or observed though. Maybe they are here. Maybe we are the aliens without knowing. I’m getting ahead of myself though. Here’s another similar idea to UFOs being alien spacecraft:
They’re Here But We Haven’t Noticed
This one is something of a mental health hazard because it very much stimulates paranoia, and again there are several versions of this. The closest one to the previous explanation is that there are indeed alien spacecraft, or perhaps nanoprobes, visiting or monitoring this planet but we can’t detect them, or haven’t done so. It does make sense that if they wanted to remain hidden, they would succeed in doing so, given their level of technology. One suggested means of eploring the Galaxy is to launch swarms of minute spacecraft in order to save energy and avoid collision with dust and other bodies between the stars simply by being smaller. It would also be relatively easy to secrete a reasonably large completely visible probe somewhere in the Solar System or in orbit around Earth without attracting much attention. Another somewhat disturbing further option exists. Right now, we can do 3-D printing and have some ability at genetic engineering. We aren’t that far off inventing a replicator, should that prove possible at all, bearing in mind that things often seem easier before they’ve been done. But for a technology far in advance of our own, it should be possible not only to produce a completely convincing living human, but even one whose memories are false and doesn’t even realise they’re the product of an alien machine. In other words, we could ourselves be aliens without even knowing. This kind of prospect is very similar to the kind of beliefs many children have and also has some resemblance to Capgras Syndrome. Whereas all of these things are possible, they are almost by definition non-scientific as they have no way of being falsified. Perfect camouflage is just that. No test can be performed to verify or refute that it happens. Therefore, whereas all of these things seem entirely feasible, they aren’t actually particularly meaningful as a simpler explanation for what we observe is that there are no alien spacecraft or “pod people”.
They’re Too Alien
Many answers to the Fermi Paradox seem quite anthropomorphic in one way or another. For instance, both the Zoo Hypothesis and the Dark Forest attribute perceived human-like behaviour, in opposite directions, to these unknown and possibly non-existent beings. But what if the reality is that aliens are in some way intelligent but also truly alien? What if they’re just fields of singing potatoes? They’re very intelligent, to be sure, but all of that cleverness is channelled into art so sophisticated and arcane that it can’t be grasped by humans, and also they sit there and do nothing else. They might send up a shoot or two with eyes on the end every now and again and look at the stars and planets in their night skies, but it doesn’t grab their interest. Of course, the singing spud scenario is borrowed from Grant and Naylor, but it’s one of many possibilities, some unimaginable and all unanticipated. We are one example of a tool-using species. Another one may be dolphins, and it doesn’t look like they’re going to develop our kind of technology at any point, not only because they live in the sea and don’t have anything like hands, but also because they’re just not interested, and that’s just on this planet and quite closely related to us. Or they could be a spacefaring species like some humans aspire to be but just have no concern about meeting any aliens or getting in touch with them. We might not even recognise each other as alive. For instance, what if they were a rarefied plasma drifting between the stars?
Different Or No Maths
I went into this one the other day here. Most of us humans don’t distinguish between subitising, which is the ability to judge how many items there are at a glance and which we are usually able to do about five, and the kind of activity which counts as arithmetic and mathematics. I won’t wade in here but there doesn’t seem to be any good reason why we would have evolved an aptitude to do mathematics given our lifestyle, or for that matter for any other species to do so given its niche, but we’ve done so anyway and this has somehow proven to be useful in rocket science and the like. Maybe it’s this which is missing from other intelligent life forms’ faculties, so they do fine building some kind of civilisation where everyone isn’t just a number, but they never leave their home world because they never develop anything able to do that.
Right, so this has turned out really long, so at this point I’m going to stop and publish. Part II in a bit, possibly tomorrow.
Yesterday I considered the question of what civilisation would be like if nobody could do mathematics “as we know it”, which is one fairly minor suggestion for an answer to the Fermi Paradox of “where are all the aliens?”. Of course the simplest answer to this is that there aren’t any and probably haven’t ever been any, but there are also multitudinous other possibilities, many of which have interesting implications for us even if we never make contact with any. Yesterday, the fault was in ourselves, but what if the fault was in not our stars, but the stars? What if the issue is not that other intelligent life forms lack a capacity we do have, but that there is a realistic, external but still conceptual problem which prevents anyone from getting out there into interstellar space in a reasonable period of time? What if, so to speak, science “runs out”?
Even if there are no aliens, this possibility is still important. It’s entirely possible that they are in fact completely absent but science will still stop, and that would be a major issue. It would be rather like the way Moore’s Law has apparently run up against the buffers due to thermal noise and electron tunnelling. Ever since 1961, when the first integrated circuit was invented, there’s been an approximate doubling of transistors per unit area of silicon (or germanium of course) every two years or so, which may be partly driven by commercial considerations. However, as they get smaller, the probability of an electron on one side of a barrier teleporting to the other and thereby interfering with the operation of transistors increases. In 2002, it was theorised that the law would break down by the end of the decade due to Johnson-Nyquist noise, which is the disturbance of electrical signals due to the vibration of atoms and molecules tending to drown out weak signals, which is what nanoscale computing processes amount to. It isn’t clear whether Moore’s Law has stopped operating or not because if it does, it would have consequences for IT companies and therefore their profitability and share values, so the difficulty in ascertaining whether it has is a good example of how capitalism distorts processes and research which would ideally operate in a more neutral environment, and there’s also a tendency for people to suppose that scientific change will not persist indefinitely because of being “set in their ways” as it were, so it’s hard to tell if it actually has stopped happening. It’s been forecast, in a possibly rather sensationalist way, that once Moore’s Law does stop, there will be a major economic recession or depression and complete social chaos resulting from the inability of IT companies to make enough money to continue, but I don’t really know about that. It seems like catastrophising.
More widely, there are areas of “crisis”, to be sensationalist myself for a moment, in science, particularly in physics but as I’ve mentioned previously also perhaps in chemistry. The Moore’s Law analogy is imperfect because it isn’t pure scientific discovery but the application of science to technology where it can be established that a particular technique for manufacturing transistors has a lower size limit. This is actually a successful prediction made by physics rather than the end of a scientific road. However, the consequences may be similar in some ways because it means, for example, that technological solutions relying on microminiaturisation of digital electronics would have to change or be solved in a different way, which is of course what quantum computers are for. The end of science is somewhat different, and can be considered in two ways.
The first of these is that the means of testing hypotheses may outgrow human ability to do so. For instance, one possible time travel technique involves an infinitely long cylinder of black holes but there is no way to build such a cylinder as far as can be seen, particularly if the Universe is spatially finite. Another example is the increasing size and energy required to build particle colliders. The point may come when the only way to test an hypothesis of this kind would be to construct a collider in space, and right now we can’t do this and probably never will be able to. There would be an extra special “gotcha” if it turned out that in order to test a particular hypothesis involving space travel it would be necessary to have the engines built on those principles in the first place to get to a place where it could be falsified.
Another way it might happen is that there could be two or more equally valid theories which fit all the data and are equally parsimonious and there is no way of choosing among them. It kind of makes sense to choose a simpler theory, but on this level it becomes an æsthetic choice rather than a rational one because nothing will happen as a result of one theory being true but not the other. If all the data means all the observable data, this is the impasse in which science will find itself.
It also seems to be very difficult to arrive at a theory of quantum gravity. Relativity and quantum physics are at loggerheads with each other and there seems to be no sign of resolution. There “ought to be” some kind of underlying explanation for the two both being true, but it doesn’t seem to be happening. Every force except gravity is explained using the idea that particles carry the message of that force, such as photons for electromagnetism and gluons for the strong nuclear force, but gravity is explained using the idea that mass distorts space instead, meaning that gravity isn’t really a force at all. I’ve often wondered why they don’t try to go the other way and use the concept of higher dimensions to explain the other forces instead of using particles, but they didn’t and I presume there’s a good reason for that. It wouldn’t explain the weak force I suppose. However, there does seem to be a geometrical element in the weak force because it can only convert between up and down quarks if their spin does not align with their direction of motion, so maybe. But so far as I know it’s never been tried this way round, which puzzles me. There’s something I don’t know.
There may also be a difference between science running out and our ability to understand it being exceeded. Already, quantum mechanics is said to be incomprehensible on some level, but is that due to merely human limitations or is it fundamentally mysterious? This is also an issue evoked with the mind-body problem, in that perhaps the reason we can’t seem to reconcile the existence of consciousness with anything we can observe is that the problem is just too hard for humans to grasp.
People often imagine the ability to build a space elevator, which is a cable reaching thousands of kilometres into space to geostationary orbit up and down which lifts can move, making it far easier to reach space, but there doesn’t appear to be a substance strong enough to support that on Earth, although it would be feasible on many other planets, moons and asteroids using existing technology. We might imagine it’s just round the corner, but maybe it isn’t. Likewise, another common idea is the Dyson sphere, actually acknowledged by Freeman Dyson himself as having originally been thought of by Olaf Stapledon, which encloses a sun in a solid sphere of extremely strong matter to exploit all of its energy, which again may not exist. And the obvious third idea is faster than light travel, which is generally taken to be impossible in any useful way. One way the search for extraterrestrial intelligence (SETI) could be conducted is to look for evidence of megastructures like Dyson spheres around stars, and in one case a few people believed they’d actually found one, but what if they turn out to be impossible? Dyson’s original idea was a swarm of space stations orbiting the Sun rather than a rigid body, which seems feasible, but an actual solid sphere seems much less so. Our plans of people in suspended animation or generation ships crossing the void, or spacecraft accelerated to almost the speed of light may all just be pipe dreams. Our lazy teenage boasts will be high precision ghosts, to quote Prefab Sprout. Something isn’t known to be possible until it’s actually done.
If non-baryonic dark matter exists, the beautiful symmetries of elementary particles which the Standard Model of physics has constructed do not include it. And despite my doubts, it may exist, and even if it doesn’t there’s an issue with explaining how galaxies rotate at the rate they do. However, at any point in the history of science there were probably gaps in knowledge which seemed unlikely to be filled, so I’m not sure things are any different today. It reminds me of the story about closing the US patent office in 1899 CE, which is apparently apocryphal, because everything had been invented. However, there is also the claim that technological progress is slowing down rather than accelerating, because the changes wrought in society by the immediate aftermath of the Industrial Revolution were much larger than what has happened more recently. At the end of the nineteenth century, there seemed to be just two unresolved problems in physics: the ultraviolet catastrophe and the detection of the luminiferous æther. These two problems ended up turning physics completely upside down. Now it may be possible to explain any kind of observation, with the rather major exceptions which Constructor Theory tries to address but these seem to be qualitatively different. The incompleteness of these theories, such as the Uncertainty Principle and the apparent impossibility of reconciling relativity with quantum mechanics, could still be permanent because of the difficulty of testing these theories. Dark matter would also fall under this heading, or rather, the discrepancy in the speed of galactic movement and rotation does.
This is primarily about physics of course, because there’s a strong tendency to think everything can be reduced to it, but biocentrism is another possible approach, although how far that can be taken is another question. Also, this is the “trajectory and particles” version of physics rather than something like constructor theory, and I’m not sure what bearing that has on things. Cosmology faces a crisis right now as well because two different precise and apparently reliable methods of measuring the rate of expansion of the Universe give two different results. Though I could go on finding holes, which may well end up being plugged, I want to move on to the question of what happens if science “stops”.
The Singularity is a well-known idea, described as “the Rapture for nerds”. It’s based on the perceived trend that scientific and technological progress accelerate exponentially until they are practically a vertical line, usually understood to be the point at which artificial intelligence goes off the IQ scale through being able to redesign itself. Things like that have happened to some extent. For instance, AlphaGo played the board game Go (AKA Weichi, 围棋) and became the best 围棋 player in the world shortly after, and was followed by AlphaGo Zero, which only played games with itself to start with and still became better than any human player of the game. This was a game previously considered impossible to computerise due to the fact that each move had hundreds of possible options, unlike chess with its couple of dozen or fewer, meaning that the game tree would branch vastly very early on. But the Singularity was first named, by Ray Kurzweil, two and a half dozen years ago now, and before that the SF writer Murray Leinster based a story on the idea in 1946, and it hasn’t happened. Of course a lot of other things have been predicted far in advance which have in fact come to pass in the end, but many are sceptical. The usual scenario involves transhumanism or AI, so to an extent it seems to depend on Moore’s Law in the latter case although quantum computing may far exceed that, but for it to happen regardless of the nature of the intelligence which drove it, genuine limits to science might still be expected to prevent it from happening in the way people imagine. For this reason, the perceived unending exponential growth in scientific progress and associated technological change could be more like a sigmoid graph:
I can’t relabel this graph, so I should explain that this is supposed to represent technological and scientific progress up to the Singularity, which occurs where the Y-axis reads zero.
There’s a difference between science and technology of course. It’s notable, for example, that the development of new drugs usually seems to involve tinkering with the molecular structure of old drugs to alter their function rather than using novel compounds, and there seems to be excessive reliance in digital electronics on a wide variety of relatively scarce elements rather than the use of easily obtained common ones in new ways. And the thing is, in both those cases we do know it’s often possible to do things in other ways. For instance, antibacterial compounds and anti-inflammatories are potentially very varied, meaning for example that antibiotic resistance need not develop anything like as quickly as it does, even if they continue to be used irresponsibly in animal husbandry, and there are plenty of steps in the inflammatory process which can be modified without the use of either steroids or so-called non-steroidal anti-inflammatories, all of which are in fact cycloöygenase inhibitors, and there are biological solutions to problems such as touchscreen displays and information processing such as flatfish and cuttlefish camouflage which imply that there is another way to solve the problem without using rare earths or relatively uncommon transition metals. So the solutions are out there, unexploited, possibly because of capitalism. This would therefore mean that if the Singularity did take place, it might end up accelerating technological progress for quite a while through the replacement of current technology by something more sustainable and appropriate to the needs of the human race. Such areas of scientific research are somewhat neglected, meaning that in those particular directions the chances are we really have not run out of science. They could still, in fact, have implications for the likes of space travel and robotics, but it’s a very different kind of singularity than what Kurzweil and his friends seem to be imagining. It’s more like the Isley Brothers:
Having said that, I don’t want to come across as a Luddite or anti-intellectual. I appreciate the beauty of the likes of the Standard Model and other aspects of cutting edge physics and cosmology. I’m not sure they’re fundamental though, for various reasons. The advent of constructor theory, for example, shows that there may be other ways of thinking about physics than how it has been considered in recent centuries, whether or not it’s just a passing trend. Biocentrism is another way, although it has its own limits. This is the practice of considering biology as fundamental rather than physics. The issue of chemistry in this respect is more complex.
Returning to the initial reason this was mentioned, as a solution to the Fermi Paradox, it’s hard to imagine that this would actually make visiting other star systems technologically unfeasible. If we’re actually talking about human beings travelling to other star systems and either settling worlds or constructing artificial habitats to live in there, that doesn’t seem like it would be ruled out using existing tech. The Dædalus Project, for example, used a starship engine based on the regular detonation of nuclear bombs to accelerate a craft to a twelfth of the speed of light, though not with humans on board, and another option is a solar sail, either using sunlight alone or driven by a laser. Besides that, there is the possibility of using low doses of hydrogen sulphide to induce suspended animation, or keeping a well-sealed cyclical ecosystem going for generations while people travel the distances between the stars. There are plenty of reasons why these things won’t happen, but technology doesn’t seem to be a barrier at all here because methods of doing so have been on the drawing board since the 1970s. Something might come up of course, such as the maximum possible intensity of a laser beam or the possibility of causing brain damage in suspended animation, but it seems far-fetched that every possible technique for spreading through the Galaxy is ruled out unless somewhere out there in that other space of scientific theory there is some kind of perpetual motion-like or cosmic speed limit physical law which prevents intelligent life forms or machines from doing so.
All that said, the idea that science might run out is intriguing. It means that there could be a whole class of phenomena which are literally inexplicable. It also means humans, and for that matter any intelligent life form, are not so powerful as to be able to “conquer” the Cosmos, which is a salutory lesson in humility. It also solves another peculiarity that somehow we, who evolved on the savannah running away from predators, parenting and gathering nuts and berries for food and having the evolutionary adaptations to do so, have developed the capacity to understand the Universe, because in this scenario we actually haven’t.
Zubanelchemale, as I call it, may be a quite remarkable star. Incidentally, the name, which is Arabic, can be spelt in various ways and the way I spell it might be quite old-fashioned. Zubeneschamali is another spelling. It means “the northern claw”, from الزُّبَانَى الشَمَالِي , and an accompanying star from our perspective is Zubenelgenubi, “the southern claw”. It might be thought from the name that these stars are in Scorpio or Cancer, and they are in fact next to Scorpio, but it appears that over the centuries what used to be thought of as the scorpion’s claws are now considered a pair of scales, since they are now considered part of Libra. Zubenelgenubi is actually a double star, designated α1 and α2, and this is significant because of the remarkable thing about β Libræ, Zubanelchemale, which is that some observers say it’s green. To my naked eye plus glasses, it does actually look slightly green.
Although other stars are reported as being green, they’re usually binary or multiple systems, such as Rasalgethi and ζ Piscium, both of which are multiple. The latter is in fact quintuple. The reason for their apparent colours is probably the contrast with the colour of their companions. The peculiar thing about Zubanelchemale is that it is an unaccompanied star with which there is no contrasting companion to make it look green. In fact it may have a companion but it can’t be seen from here if it has. It isn’t always seen as that colour and there seems to be no explanation for it. It’s a B-type star, making it hotter than the white A-types, but this should make it blue-white if anything rather than green. Because there are no green stars, so it’s said.
This sounds like a really sweeping statement. However, without immediately going into the astrophysics of the situation, it’s relatively easy for astronomers to observe millions of stars in this galaxy and many in other galaxies, and whereas we are somewhat stuck to stars in our own galactic neighbourhood for here, the same doesn’t apply to other galaxies, which can often be seen more or less in their entirety. It isn’t like looking for planets or megastructures. Every star has a window onto the Universe through which it can be seen unless there’s something obscuring the view. Clearly distance leads to stars being too faint to see, but it seems a fair assumption that the stars we can see in our own galaxy along with the ones visible in those nearby are a representative sample of the stars in the Universe, and with the possible, but likely illusory, exception of Zubanelchemale, none of them are green.
I would, though, add one caveat to this which applies to extremely distant stars. Space is expanding, and more distant objects are receding from each other faster than relatively nearby ones. This causes the Doppler Effect to influence the colour of the light such objects emit, meaning that presumably a very distant blue supergiant might look green. However, it would also be too far away to see as an individual star, and from a low velocity relative to it, it wouldn’t look green.
As well as observation, basic astrophysics can be used to demonstrate why there are no green stars. As an object heats up, it emits infrared radiation at shorter and shorter frequencies, until eventually it’s hot enough to glow visibly red. It then becomes orange, yellow, white and blue-white with increasing temperature, as the wavelengths at which it radiates enter the visible spectrum. But these are along a band. The red glow is not isolated but accompanied by infrared light which we can’t see, and the colours of stars, and most hot objects in fact, radiate across a range of frequencies rather than pure colours like a laser or an LED would, and consequently they are never green. There is a point at which the brightest colour is green, but it’s swamped by the other colours being radiated. There are therefore no green stars.
That’s the standard explanation, and it makes a lot of sense, but there’s something it seems to have failed to take into consideration: there are in fact luminous green objects in space, along with purple ones, which would also be impossible for an object glowing simply beause of heat to do. A fairly well-known example is Hannys Voorwerp:
“Voorwerp” is just the Dutch for “object”. This was found as part of the Galaxy Zoo project, which presents images of galaxies to the general public for them to identify and classify. Hanny is Hanny van Arkel, a schoolteacher. The galaxy at the top of the picture is referred to as IC 2497, and is 650 million light years away in the constellation Leo Minor. The Voorwerp is a burnt out quasar which would have been visible from here early in the last Ice Age, and is around sixty thousand light years from the galaxy in question. A quasar is a relatively small object which gives out as much radiation as a thousand galaxies. They used to be thought to be inside our own galaxy because they’re so unfeasibly bright that they surely couldn’t be gigaparsecs away, which many of them are, but they nonetheless are. This confusion turns up in the Star Trek TOS episode ‘The Galileo Seven’, where a quasar is depicted in the Alpha Quadrant. They consist of supermassive black holes surrounded by gaseous discs constantly falling into them and generating light through friction and extreme gravitational pull just outside the event horizon. This object is a trail of gas pulled out from a galaxy IC 2497 was passing and then ionised by a quasar at the centre of the galaxy through the radiation it was emitting. Although it’s gone out, the electromagnetic radiation is still in transit to the object, causing it to glow green. This is known as a quasar ionisation echo. Normally this would be hidden by the glare of the quasar. Around one and a half dozen such objects have since been found in the Galaxy Zoo data. There’s a new class of galaxies based on them called “pea galaxies” because of their colour, and the reason they’re green is that they contain doubly ionised oxygen, which emits primarily cyan light.
This emission of green light is, though, known as a “forbidden mechanism”, because in normal circumstances it can’t happen. It can, however, happen in places such as Hannys Voorwerp because the individual atoms and molecules of the gases are far apart enough that they never collide, as they are in the upper atmosphere of Earth and the lunar atmosphere. This means that when atoms are energised, they will release that energy in unusual ways, such as the greenish light emitted by doubly ionised oxygen. Similar or the same phenomena can be observed in nebulæ and aurora polaris. Oxygen is the third most common element in the Universe taken as a whole. It used to be thought that the light emitted by these mechanisms was an element referred to as “nebulium”, rather similar to the discovery of helium on the Sun before it was discovered here, but it turned out to be oxygen in an unfamiliar state.
Hence, although there are no green stars, there are plenty of luminous green objects in space. There are also green planets, or at least greenish ones, such as Uranus:
Although Uranus is hardly viridian, this comparison to Neptune to his right clearly shows the green tinge. Uranus is that colour due to methane in the atmosphere, and clearly isn’t very green.
However, I do suspect there would be a fairly straightforward way for a star to become green. There doesn’t seem to be any reason why a star wouldn’t be surrounded by a sparse cloud of gas relatively high in oxygen which it could then excite with its radiation, causing it to glow green, although the problem there may be that a star bright enough to do that would drown out the green tinge. Alternatively, maybe a so-called “brown dwarf” could be green due to having an atmosphere of this nature filtering out the red and blue light. It really does not seem to be such an unlikely set of circumstances that not one single star humans can observe in the entire Universe looks green.
Although for some reason no process superimposed on the unimpeded light from any star seems to have turned it green, it would be relatively simple for an advanced civilisation to erect some kind of filter or create some kind of process which would do so. This hasn’t happened either, and these two facts taken together may have some significance. Firstly, the absence of an apparently fairly straightforward process which would make a star green indicates that even in such a large Universe, not all things which are possible actually happen. That could apply to life, complex life or the appearance of intelligence as well. Maybe that’s only happened once, and this too is suggested by the absence of green stars. If intelligent entities wanted to advertise their presence in the Universe, they could do so by making a star green. The absence of such stars might mean there is no other intelligent life in the Cosmos. Or, it could mean that it’s dangerous, or perceived as dangerous, to give potentially hostile aliens a “go” signal, as it were, or that all successful spacefaring civilisations have a sense of environmental responsibility to leave stars as they found them, or that they wish to hide their presence from more primitive civilisations due to something like the Prime Directive.
The other notable non-occurrence of green is among mammals, but that’s another story.
Yesterday I mentioned in passing the concept of super-habitability. I’m happy to say that ‘Handbook For Space Pioneers‘ introduced this concept, although it may have passed unnoticed. In this book, which describes the eight habitable planets available for human settlement in 2376 CETC (Common Era Terrestrial Calendar), the final planet, Athena, 77.6 light years from Earth in the HR 7345 system, is actually more habitable than Earth. The book rates the different planets according to their habitability using the ‘Von Roenstadt Habitability Factor’, with the least habitable, Mammon, having one of 0.79. This is a largely desert planet with a thin atmosphere which was largely settled due to its rare earth metals, which are useful in matter-antimatter reactors. Earth has a factor of 1.0, and Athena one of 1.09. This is because Athena is not only similar to Earth but lacks a polar continent, meaning that more of its land is hospitable to human settlement. Therefore it was this book that came up with the idea. Ahead of its time.
The search for exoplanets tends to be biassed in various ways as I’ve previously mentioned. One of these is that the ideal planet to be detected would be a super-Jupiter orbiting very close to its rather dim star, orbiting parallel to the line of sight. This is indeed a very common type of planet to be found but not at all Earth-like. It also gets a bit depressing after a while because the planets concerned may make their systems unsuitable for more hospitable planets further out. This situation has been somewhat remedied more recently and many somewhat Earth-like planets have now been found.
However, it’s been suggested that we may be setting the bar too low here. I mentioned the Copernican principle yesterday, also known as the principle of mediocrity, that it’s often informative to look at the world with the assumption that there’s nothing special about us as a species, and perhaps more closely, apply the same principle to ourselves as individuals (e.g. “accidents always happen to someone else until they happen to you” – this is not some kind of exaggerated humility and self-effacement). When we look for Earth-like planets, we are in a sense only looking for worlds which are good enough, and also good enough for humans, as opposed to worlds which are fantastic. That is, Earth is all very well, and yes it is precious and rare and all the other stuff, but there could in principle be worlds which are even more hospitable to life than this one. Super-habitable planets, in other words.
I feel a sense of hesitancy here because it’s like insulting my own mother, but the fact is that this planet may be particularly suitable for humans, but it could have, and has been in the past, more comfortable for life than it was when we first evolved as anatomically modern humans. At that point, it was plagued by regular ice ages, had larger deserts and had little in the way of continental shelves, meaning that fishing, for example, would’ve been very difficult without boats in most places. Not that I care, as a vegan, but there is a theory that I accept that we went through an amphibious phase when we depended on sea food, which could be relevant to the development of the our brains and ability to speak. Even now there are issues with this planet regardless of the influence of humans on it. Looking beyond humanity confronts us with the fact that although this planet is really quite a nice place to live, it may not be ideal for other life. There are two aspects to this as well. One is “life as we know it”. That is, life which breathes oxygen, drinks water, uses sunlight to synthesise food, is carbon-based and depends on biochemistry, which may not be the only kind of life. We don’t know that there cannot be other forms of life which are very different, to which Earth would seem a very hostile place. For instance, it’s easy to imagine aliens detecting the high level of corrosive and hyper-reactive free oxygen in our atmosphere and concluding that this is not the best abode for life because they have simply never encountered body chemistry which actually requires that. They might feel the same way about this place as we would about a planet whose atmosphere was high in elemental fluorine or chlorine and had seas of aquæous hydrofluoric or hydrochloric acid. Or, if there were life forms based on plasma, and I strongly suspect this can happen, they might wish to avoid anywhere with even a trace of liquid water in its atmosphere or on its surface and only survive in the very driest deserts here. But the current popular conception of superhabitability is to be biocentric in the sense of looking for the ideal conditions for life to begin, develop and thrive on it. Perhaps surprisingly, Earth is not currently ideal for this, and it isn’t even entirely due to human technological development. Moreover, Earth has been more habitable in the past that it currently is.
Seventy-one percent of Earth’s surface is underwater, and of that most of it is so deeply so that no daylight ever reaches the ocean bed. This doesn’t rule life out at all of course – there is life in the deepest part of the ocean – but it does reduce the energy available and there is less diversity down there than elsewhere. It relies on food raining down from further up, sometimes including dead whales, which provide a huge amount of nutrition for quite some time. The water column above the beds is also rich in life, getting richer the closer to the surface it gets, and there are of course ecosystems around hot water vents at the bottom of the ocean. However, the euphotic zone, where there’s enough light for photosynthesis to take place, is only two hundred metres deep, and that’s where the ocean teems with life. Shallow seas are much richer in life and more diverse for that reason. Hence, withough being disrespectful of the ecosystems of the trenches, abysses and abyssal plains, more than half of the surface of this planet could be said to be “wasted”. Two ways in which things could be different here are for the seas to be shallower. The shallow sea biome is quite rare nowadays on Earth, but in the past has been much more extensive, and would mean that plants could grow on the bottom of the sea and support many other organisms. The same could apply to another possible situation, where the Sun was either brighter or we were closer to it, meaning that although there might still be extensive abyssal plains, the light would penetrate further down. Alternatively, photosynthesis, which currently operates using red light, could possibly be based on shorter wavelengths which penetrate further. A planet with a red photosynthetic pigment, for example, might have seaweed growing deeper. It’s possible that chlorophyll only appeared on this planet because a preceding purple pigment used by another taxon of organisms meant that only red light was available to plants, and if that second stage hadn’t happened, “plants” would now mainly be purple.
Stars are also different colours. From the viewpoint of photosynthesis, this could also have implications for the colour of the pigments. Habitable planets were long thought only to be possible for worlds associated with F-, G- or K-type stars but it’s now thought that red dwarfs may be more suitable (for a summary of spectral types, look here). K-type stars last longer on the Main Sequence and are orange, so I presume a planet orbiting one would be in a constant “rosy-fingered dawn” situation, though much brighter, but this gives life longer to evolve than it does here. Our own planet will be able to support microörganisms for up to 2 800 million years in the future, but these will to some extent resemble the æons when only microbes existed here. Large multicellular life is likely to become extinct only about 800 million years hence when there won’t be enough carbon dioxide in the atmosphere to support photosynthesis, which will happen due to the increasing brightness of the Sun. This is also driven by plate tectonics, as carbonate rocks are forced from the sea bed into the mantle where they react and release carbon dioxide while forming silicates. This means that a fainter, more long-lived star or more active continental drift would make this planet more hospitable to life for longer.
A larger planet would often have a number of advantages for life. Here I’m talking about rocky planets rather than gas giants. This is where the biocentric approach becomes more evident. The definition of a “superhabitable” planet here is to do with how suitable it would be for life of the kind we’re currently familiar with rather than humans, because large, dense planets would have higher gravity than Earth. LHS 1140b, for example, may be superhabitable, but not for us. It’s seven times the mass of Earth and 40% larger in diameter, giving it a surface gravity more than three times ours. This is beyond the capacity of human beings to survive unaided without some form of modification, but its dense atmosphere may provide it with a greenhouse effect which heats it to a temperature compatible with life as found here. Larger rocky planets will take longer to cool, meaning that there will be more active plate tectonics and more carbon dioxide recycling, although there may be a limit here because higher gravity would slow it beyond a certain point due to the weight of the continental plates. Larger planets, particularly fast-rotating ones, would have stronger magnetic fields and therefore be more easily able to hang on to their atmospheres and protect the surface from ionising radiation.
When Earth has been warmer, there has been more biodiversity, although just to comment on anthropogenic climate change that doesn’t work out now because it’s a rapid change and also unstable. Evolution might eventually fill in the gaps of course. This planet has a tendency to edge into colder conditions rather than hotter ones, for instance the current spate of ice ages and the Snowball Earth scenario in the late Cryptozoic Eon, but most of the time it’s been hotter on average than it is today. Consequently we’d’ve done better if we were somewhat closer to the Sun, although it’s not clear how much, at least to me. Another circumstance where there’s been more diodiversity and larger animals has been when oxygen was higher in the atmosphere, although this has a limit above which there would be devastating fires and other oxidative damage. The highest partial pressure of oxygen ever on this planet has been 350 millibars, amounting to 35% of the atmosphere, but in a denser atmosphere this proportion would be smaller because the absolute quantity of oxygen is what matters, not the proportion.
The final helpful criterion is a combination of about the same water cover combined with a larger number of landmasses. Earth currently has six continents, one of which is circumpolar. At other times it’s had as few as one. I’m not sure why this is considered advantageous but I can make a few guesses. It would mean that evolution would take place in isolation on each of the continents, as it has here with Australia, South America and the rest of the non-polar continents taken together, and that arid areas would tend to be smaller, although rain shadow deserts would still exist. Those, however, would be less common as well because there would be fewer mountain ranges due to fewer continents crashing together. There would also be more land near the coast than there currently is here, and more shallow sea areas on continental shelves. I’m reminded of Douglas Adams and his description of Ursa Minor Beta as consisting largely of beaches.
Some of these characteristics are impossible to detect with existing technology. For instance, although I think there is a way of finding continents and mapping them crudely by measuring fluctuations in brightness and colour, only a very few planets have even been imaged as points of light so far and they’re much larger than Earth. There’s probably a way of coördinating and processing telescope images taken in different parts of the Solar System to simulate the effect of an enormously magnifying lens, but I’m just guessing there. Nonetheless, there are certain known planets which do appear to satisfy some of these conditions. One is Kepler-442b. Incidentally, many of these planets have rather boring, monotonous names at present because they were all found by the same project. This planet, also known as KOI-4742.01 orbits its K-type sun at a distance of 61 200 000 kilometres once every 112.3 days, has a mass 2.3 times Earth’s and a diameter of around 17 100 kilometres. This gives it a surface gravity twenty-eight percent higher than ours, which is just about bearable. Without other factors being involved, its surface temperature would be about -40, but it could easily be warmer due to the Greenhouse Effect, low albedo and so forth. This last factor is of course the way in which it isn’t super-habitable, if it’s so.
It’s possible that there are more super-habitable planets than strictly Earth-like ones because there are more orange dwarfs than yellow dwarfs. Nine percent of stars in the Galaxy are of this kind as opposed to seven percent of the Sun’s spectral type, and several of the criteria simply follow from a planet being more massive than Earth. For instance, higher gravity could make the oceans shallower and give the planets more tectonic activity, and as a personal interjection continents on larger planets have more chance of being widely separated and having different evolutionary histories. A planet 1.4 times the diameter of the Earth whose surface is 29% covered in land, i.e. proportionately the same as Earth’s at the moment, has almost twice as much land, which if the average continent size were the same would be represented by a dozen continents. Likewise, we currently have five oceans here but there could be more there, although oceans are not well-defined and in a sense there is only one ocean. Planets with more than fifty percent land coverage could have landlocked oceans, and even worlds with less land due to quirks of geography, but this won’t apply to planets of this kind.
What might such a planet be like? Here I’m going to choose an example which satisfies all the criteria. There will be many others, if they exist at all that is. The average temperature would be somewhat higher than Earth’s and there would be no permanent ice caps at the poles, although snow-covered mountains and glaciers could easily exist. The climate would be warm and humid, with more cloud cover than Earth. Tropical rain forest vegetation would cover much of the land and there would be smaller desert areas. The oceans would be shallower and there would be copious vegetation on the sea beds. Atmospheric oxygen content would be higher in absolute terms but lower in terms of percentage than Earth’s. The denser atmosphere would mean stronger winds and more devastating rotary storms such as tornados and hurricanes. Also, these planets are likely to be more similar to each other than strictly Earth-like planets would be. The general picture is a little similar to the way Earth was at the climax of the age of dinosaurs or during the Carboniferous, although the higher gravity would limit the size of terrestrial megafauna.
These larger planets have a kind of momentum to them, which allows them to continue with fairly stable climatic conditions for many æons. By contrast, Earth-like planets run the risk of becoming permanently ice-covered, tipping into runaway Greenhouse effects and ending up like Venus, losing much of their atmospheres or relying more on large moons to maintain their magnetic fields, and therefore perhaps the ones that don’t have them or something else to raise internal tides only have thin atmospheres and no land life.
However, this does raise another question in my mind. As far as we know, we are the first technological civilisation to arise on this planet, although there’s tantalising evidence that there may have been advanced industrial processes here during the Eocene, maybe not from terrestrial species. If that’s so, it means that the periods of time during which Earth was more hospitable to life than it is today didn’t give rise to tool-using species. Therefore, is it possible that a more hospitable habitat is like the Swiss with their cuckoo clocks? Would stability end up providing little challenge to species and prevent it from evolving humanoid intelligence? Are these planets too comfortable? And there’s another question. Although these planets seem stable, they would be nearer a set of limits for biological habitability. Our planet has issues, but maybe that’s a sign of it being able to endure change. If something happened to one of these planets, like a large asteroid impact or a change in the luminosity of the sun, would this proce too much for life to handle? For instance, on this planet the life could be replenished by that surrounding undersea vents even if it died elsewhere, but I’m not sure whether there’d be many extremophiles – organisms who prefer hostile conditions – on such a world. Also, these planets are superhabitable by the needs of life as we know it in general, but not by human standards. We’d do okay, probably, on a planet which was somewhat larger and warmer than Earth although we’d have to be wary of the storms, but these super-habitable worlds wouldn’t be pleasant places to live for us. There’s a potential second set of hypothetical planets which are super-habitable for us, for instance with the Galactic Association example of Athena, a planet with no polar continent. Some of the characteristics would be similar, such as smaller but more numerous continents, but the set of criteria is not the same.
Taking this the other way is even more speculative because we’re only aware of one example of how life can arise and evolve, which is based on chemistry, organic matter, water and to a lesser extent oxygen for respiration. If there are other ways for life to exist, there could be whole other sets of “habitable” environments – I hesitate to say “planets” here because for all I know this would be happening on the surfaces of neutron stars, in nebulæ or the photospheres of “ordinary” stars. This is rather more difficult to discuss, but if life can exist in different ways it would seem to multiply the probability of life in the Universe, and also of the types of world which could support it. But I can only really leave this as a possibility thus far, or at least without making this post really long.
To conclude then, all this looks rather cheerful as regards the possibility of life as we know it in the Universe, but it also kind of pushes us Earthlings into a corner, as if all of this is true, we’re quite atypical of life in the Universe and our planet’s a bit weird. So who knows?
. . . but not all! There’s Skippy, Lassie and Judy from ‘Daktari’, and there are even non-living actors such as that soft toy in ‘The Double Deckers’. Most writers are also human, as TVTropes observes. Generally, then, you get the choice of depicting aliens on telly or film by using human actors or nobody, although they do sometimes show alien “animals”, which are probably dogs most of the time. ‘Star Trek’ is of course a major offender in this area, but ‘Doctor Who’ not only shows human aliens a lot but they also all seem to be English. Then there’s ‘Star Wars’. Even when aliens are supposed to be non-humanoid, they can end up looking pretty much like us. But how realistic is this?
First of all, how realistic is the idea of life anywhere at all apart from Earth? I know I’ve been into this many times, and it’s important not to be guided by optimism or pessimism here, but realism. Many people claim that Earth has just been exceedingly lucky in retaining its life and evolving complex life, and even in our own history there’s the issue of not much at all happening until the Cryogenian at least, then a huge flurry of activity from the Ediacaran onward, along with a series of mass extinctions which at their worst wiped out 96% of all life, at the end of the Permian. In case you’re not familiar with these geological periods, it amounts to the 4600 million years of this planet’s history having no life, then apparently simple and mainly microscopic life, for seven eighths of its history. This could mean that it took evolution most of the time life has been around to stumble upon some event which accelerated it into the more complex forms which include our species, and even then it was subject to catastrophes such as being hit by asteroids and having gamma ray bursts convert much of the atmosphere into concentrated nitric acid.
The trouble is that we have just one known example, and all it’s really possible to conclude from it is that life exists in the Universe because it exists here. Unfortunately that doesn’t mean it exists anywhere else. The Rare Earth hypothesis focusses on the various things which seem to make life unlikely. For instance, although there are 125 thousand million galaxies in the observable Universe, the Milky Way may be unusual due to being unusually “quiet”, with fewer collisions and an optimally active central black hole. The Sun’s orbit round the Galaxy is particularly circular and mass extinctions have tended to coincide with the Solar System crossing a galactic arm. The distance from the centre is also optimal in that there are more heavier elements in the arm stars the closer they are to the nucleus and so life as we know it, which incidentally is what I’m talking about here rather than, say, possible plasma-based life, is more likely here, and the denser packing of the stars towards the centre makes collisions more likely, so it’s possible that as you get towards the centre the planets are being constantly pelted with comets and asteroids all the way through their existence rather than just at the beginning as happened here. Then there’s a problem with the orbits of planets in other solar systems. It’s clear that there are many “hot Jupiters”, although the method of detecting planets by looking for transits (basically eclipses) is biassed towards finding large, close planets. There are still a lot of them, and if, for example, they migrated inward they would probably have disrupted the orbits of Earth-like planets in the process of doing so. It may also be that the planets in this solar system have unusually circular orbits. Mercury has quite an elliptical one, and Pluto, though it is not currently considered a major planet, has about the same eccentricity, but on the whole they’re quite close to being circular, particularly Venus which is even closer to a circle than Earth. More elliptical orbits are likely to be less stable as well as leading to climatic extremes.
Clearing all that aside though, Isaac Asimov and others estimated that there were probably about six hundred million habitable planets in this Galaxy, or rather, planets which would become habitable at some stage. Many of these would be too young. It’s also possible that oxygen would not be produced in their atmospheres by photosynthesis. It’s been worked out that a mutation to release chlorine from sea salt instead is another possibility, and that may or may not be suitable for respiration, and a planet with no breathable atmosphere is still compatible with life, since that was Earth for most of our history. One problem with chlorine is that it’s a “dead end”. Its atoms can only form one bond, so the situation here where oxygen is part of a ring or has two bonds with another atom couldn’t exist in that kind of biochemistry. Chlorine would mainly be an oxidiser for respiration and wouldn’t contribute much to variety among organic compounds. Also, it would make the ocean extremely alkaline for this to happen, which renders a lot more compounds acidic. Asimov’s estimate may be obsolete because rather surprisingly, the most common type of star in the Universe, the red dwarf, has been found to be a suitable abode for life as we know it because a planet orbiting close enough to have locked its rotation, leaving one side in constant daylight and the other eternally dark, turns out to have a likely zone of temperatures hospitable to life in its twilight zone, so this could bump the numbers up a lot, or even multiply them. However, the fact remains that in our random sample, Earth, we find ourselves orbiting a yellow dwarf star at a distance of around 150 million kilometres, so the question arises of why we are here rather than living in the twilight zone of a planet orbiting near a red dwarf. Therefore I want to assume there are 600 million potentially habitable planets in the Galaxy and ignore the red dwarfs.
Animal life became possible on the land on this planet around 500 million years ago, although the likes of tardigrades were probably around before this accidentally, for instance if they were in a body of water which dried up seasonally they would be technically on land but dormant. It’s estimated that life will be wiped out on this planet by about 2 800 million years from now, by which time protected environments such as lakes on top of mountains or water deep underground will have boiled away, but long before that, complex life will have become impossible, so it’s thought, although I do wonder because it seems like evolutionary pressure will be extreme as Earth becomes more hostile and that something new would emerge. Leaving that speculation aside, photosynthesis will cease by around 800 million years from now and therefore any surviving life will take on very different forms even if it remains complex. I have to confess that I don’t fully understand why this will happen although I know it’s to do with carbon dioxide falling below the point where chloroplasts can use it, because I don’t know why this fall would take place, but I’m just going to accept that. The Sun will become a red giant 5 400 million years from now, giving the Earth a total life span of ten thousand million years. Over that time, it appears that complex terrestrial animals will exist for 1 200 million years, which is an eighth of that period. Consequently the currently viable number of planets falls from 600 million to forty-eight million at any one time assuming the Sun is average for a star with life-bearing planets or moons nearby. This assumption, however, may be wrong because smaller stars are more common than larger ones and they last longer and age more slowly, so it may be that most complex life is found in systems whose stars are somewhat smaller and cooler than ours. Again the question arises of why we are here, but again the answer is unavailable due to the minute sample size of one.
It’s now feasible to consider the likelihood of humanoid aliens. Up until recently, I’ve always assumed it was practically impossible for this to happen even if the Universe is full of intelligent life. The problem can be stated as follows. Suppose every beneficial mutation has two equally probable possibilities of happening which are almost equitable in improving fitness in a given situation. On forty-eight million worlds, that would be enough to provide a unique life form after only twenty-six steps. If evolution results in tool-using sentient terrestrials as a result of a random walk like the meanderings of a particle undergoing Brownian motion, this idea has more validity, and it would be supported by the possibility that sentience is a “bad idea”. Sentience for humans requires small brood sizes and a long childhood, which reduces the ability to populate an unexploited environment quickly, and it’s also been argued that sentience is self-defeating because it leads to environmental change incompatible with the survival of the species concerned. This would mean that the ability to become technological may not be particularly selected for and could therefore have a more random element to it. But we can look around at the animals on our planet and see perhaps three dozen phyla representing body plans, only a quarter or fewer of which are currently represented by more than a handful of species, and even in our own phylum there are markèdly alien-looking forms such as sea squirts:
These animals start off as tadpoles.
The question is, therefore, what are the chances of even producing vertebrates, let alone humanoids?
I’ve mentioned many times before that there was a time, getting on for 600 million years ago now, from which only one chordate fossil has been discovered as opposed to a large number of priapulids. This was Pikaia:
These were much more successful at the time than Pikaia, and Stephen Jay Gould suggested that it was pure happenstance that the ancestors of fish survived and the priapulids went into decline (they had a reputation of being the smallest phylum of all until recently).
Nonetheless, the very form of a priapulid suggests that certain shapes of animal are more likely than others. Humans have, of course, an organ which is similar in shape and there are also acorn worms:
These too are, incidentally, fairly close relatives of vertebrates, and the three-part body form still exists in our internal anatomy – the three parts of our brains are probably related to their own body shapes. Acorn worms are to us like someone took the genes we have as humans and tried to make a completely different kind of animal out of them. They have gills like fish, and like humans as embryos, sometimes hundreds of them. They smell of iodine compounds because like us they secrete them, but on the outside rather than in the thyroid, and the genes that lead us to develop a forebrain, midbrain and hindbrain instead in them lead to, well let’s be frank, the glans, the foreskin and the shaft, as it were. A basic underlying similarity has gone in drastically different directions here.
There are plenty of repeating independent patterns in evolution. One of the most striking ones is the remarkable similarity between brachiopods and bivalves. Brachiopods are now a minor phylum but used to be much more widespread. Here are some examples:
These are not molluscs. They have nothing to do with molluscs in fact. We are about as closely related to scallops and cockles as they are. Nonetheless they look remarkably similar because their lifestyles are similar. They’re sedentary filter feeders. There are also a remarkably large number of animals, and even a few plants, that look like flowers. It’s a fairly good bet that if multicellular life is common in the oceans of Earthlike planets, so are bivalve and sea anemone like animals. Convergent evolution is a thing.
Nonetheless, vertebrates are unusual. It’s unusual for animals to have hard internal skeletons. They’re much more likely to have shells of some kind. Of those that have, namely sponges and I can’t think of any others, the function of that skeleton is not to aid movement but to hold them in place. And of course we’re the only animals with spines by definition. There are plenty of animals among the minor phyla who are similar to each other in spite of not being closely related, so for example hard exoskeletons are common and have evolved independently many times.
It isn’t looking very likely that there could be humanoid aliens. But I’m not so sure.
It’s very likely that there are various complex structures on other planets which are also present here. There are less complex ones such as volcanoes, lava tubes, rivers and lakes, and the valleys and hills they carve out. There are also plenty of crystals, pebbles and the like. Structures as complex as these desert roses:
Bob Lavinsky
These are of course very like cultivated roses, my point being that inorganic processes can throw up similar structures. It’s likely that there are places all over the Universe with desert roses. Another aspect of these is that they’re baryte whereas many others are gypsum – the precise composition is not the only possibility. And then, of course, there are actual roses made of water and various organic compounds. What’s happened here is that the nature of this Universe and matter within it dictates the form of the structure. Other Earth-like planets would have oceans, thunderstorms, auroræ and the like. The shape of landmasses on this planet, such as the vaguely triangular Afrika and South America and the large number of islands which are roughly the shape of Sri Lanka, Madagascar, Sardinia and Corsica, even suggests that an Earth-like planet with land covering, say, a third of its surface, might even have something like a vaguely Afrika-shaped continent with a Madagascar-like island offshore.
The lives of identical twins separated at birth can sometimes be spookily similar, even to the extent of having the same breed of dog with the same name. This is clearly due to various social pressures and trends interacting with their biology, and although it looks like a paranormal connection it probably isn’t. We’re not so used to these things in the human world as elsewhere, although it is remarkable, for example, that both the Mayans and the Ancient Egyptians were pyramid-building cultures which worshipped the Sun and wrote in hieroglyphics, so these things do happen. Among hominids, there’s an example of an ape who evolved in the Balkans who was thought to be related to us humans because of having so many features in common but turned out not to be. In this situation, the pre-existing conditions were also in place. Apes had already evolved.
It may be that pre-existing conditions predisposing to humanoid evolution would exist elsewhere. The physical conditions of the Universe, and of planets where terrestrial life forms evolve technology, assuming they exist, may be similarly dictatorial. In particular, to us it seems that limbs with fingers and thumbs are particularly useful, and these have evolved independently a few times, in monkeys and ourselves, koalas and dinosaurs. Koalas have two thumbs, which is an unusual condition among humans. However, an elephant’s trunk would seem to do the job pretty well too, as would a series of prehensile extensions to the lips, which in fact could even be more likely as it would go along with having speech organs. There are a few other things which make it more likely.
We are bilaterally symmetrical, bipedal, live on land, speak, have largely hairless skin and hard internal skeletons. We also have four limbs and forelimbs with opposable thumbs. If there is, out there somewhere, a world with a whole class of bipedal animals with erect posture, and that’s not too far-fetched as even here we have the bipedal birds, it seems likely that any technological species which evolved in that class would have that head start in approaching a humanoid appearance. If it was also ectothermal, requiring heat from the external environment, it could have naked skin like ours. It’s a little less likely that it would have arms, and the probability of it being bilaterally symmetrical, which is more or less implied by it having two legs, is unknown. It might well be neckless and have a different respiratory pigment such as the blue haemocyanin, which crops up a couple of times independently. Given a Universe where life is common, it’s possible that technological sentient life would look humanoid at least some of the time, particularly if it’s from a world covered in hairless bipeds anyway.
This, then, is what I currently think:
It’s fair to conclude that there are around fifty million planets and moons in this Galaxy which have started out with a good chance of being suitable for life as we know it. If these survive catastrophes, which may actually stimulate evolution rather than suppress it as with, for example, our snowball Earth period which may have given rise to complex organisms, they may just have the likes of bacteria on board and we could be the exception. On the other hand, the path evolution has taken here may be common on worlds with large oceans and substantial land masses, with large complex life forms colonising the land. Given that that happens, the most improbable step to my mind is the evolution of vertebrates and of there being a major phylum including them as opposed to them being a mere taxonomical footnote. Given that that happens at all, the development of humanoids becomes much more probable. Hence what I think probably obtains in this Galaxy, provided that complex biochemical life is common on Earth-like worlds and that intelligent technological life evolves often, and those are all big ifs, is that there are a huge range of different intelligent species, but among them will be the occasional humanoid species. And if there really is an organised Galactic federation which selects species for first contact, the chances are that they will be the first species we meet. But that’s a lot of ifs. For all we know, the Universe is a barren place where only Earth has life.
A Box Of Chocolates 