Phosphorus has two main forms, or allotropes. When first extracted, it’s white and extremely toxic. The form illustrated above is red phosphorus of course. Left to itself, white phosphorus gradually turns into its red form, which is why the so-called “white” allotrope usually looks yellow:
This is not, however, supposed to be “all about phosphorus”. Rather, it’s about two issues which affect the element, both to do with life, one on this planet and one in the Universe generally.
I’ll start by explaining the importance of phosphorus to life as we know it. There are six elements making up most of the body of a living organism on Earth. These are carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus. Carbon is important because it can form chains and rings from which complex molecules can be built. It’s notable that even though silicon is far more abundant on this planet than carbon, life is nonetheless carbon-based. This is to do with things like carbon’s ability to link itself into chains, form double and triple bonds with other atoms, the fact that its atoms are small compared to silicon and the difficulty of getting silicon out of molecules such as silica which may be formed as a result of any putative biochemical processes. Carbon dioxide, the analogue of silicon, is a gas at fairly low temperatures and can be incorporated into other structures. It so happens that I do think silicon-based life is possible, but it would have to be created artificially and exist in some kind of closed environment whose contents were carefully selected. The chances of silicon-based life arising without intelligent intervention are very low. The greater terrestrial abundance of another element should be considered again here, but not right now. Hydrogen and oxygen are of course the constituents of water, a compound which is really unusual in many ways, such as its unusually high melting and boiling points on the surface of this planet, its ability to dissolve other compounds and the fact that it gets less dense as it cools below 4°C. These properties mean respectively that the chemical reactions needed for life as we know it can occur at a temperature where there’s enough energy for them to take place but not so much that they’d be unstable, that the compounds are in a liquid medium conducive to reactions in the first place and that the oceans, lakes and rivers don’t freeze solid from the bottom up. The two constituents are useful in their own right. Oxygen and hydrogen are components of countless compounds, including carbohydrates, amino acids, proteins and fats. Oxygen, unlike chlorine which has been considered as a possible alternate breathing gas for alien life, can form two bonds, meaning that it isn’t the dead end single-bonding atom which the halogens are. Nitrogen is a essential component of protein via its presence in amino acids. Amino acids have a carbon connected to a carboxyl group and an amino group, which can bond together to form chains, and a functional group such as a benzene ring or a sulphur atom which can have other biological functions. Proteins, in other words. There are also chemicals called alkaloids which occur mainly in plants and vary a lot, which have striking pharmacological effects, and the nucleotides are also rings containing nitrogen, encoding genes in DNA and RNA. Nitrogen is actually so reactive that it bonds strongly to other atoms, including other nitrogen atoms, and consequently it’s vital that various organisms can uncouple it and combine it for the benefit of the rest of the biosphere. This is known as nitrogen fixation and is performed mainly by bacteria and certain plants, and also by lightning, but if life had to rely on lightning to do this, it would not be widespread and nitrogen fixed by lightning would be the limiting factor in global biomasse. Sulphur is significantly found in a couple of amino acids and allows proteins to form more complex shapes as are needed, for example, by enzymes and hormone receptors, because they form bridges with other amino acids making the molecule tangle usefully together. It’s also found in hair, nails and various other substances such as the substances responsible for the smell of garlic and onions. Sulphur is actually a bit of an exception in the chief elements required for life because sometimes it can be substituted by either selenium or tellurium, and there are amino acids which have these elements in sulphur’s place, but both of them are much scarcer than sulphur.
Then there’s phosphorus. Phosphorus has more limited functions than the others but these are incredibly vital. It forms part of adenosine triphosphate, which organisms use to transfer energy from respiration to the other functions of the body. It also forms part of the double layers of molecules which form membranes and allow controlled and specialised environments to exist in which the chemical reactions essential to life take place, and also enables substances to be packaged, as with neurotransmitters. Thirdly, it forms the strands of sugar phosphate which hold DNA and RNA together, so even if it didn’t do anything else, some kind of method would have to exist to store genetic information. This is perhaps the least vital role though. A more restricted role is found in most vertebrates, in that it forms part of the mineral matrix of bones and teeth, but there’s plenty of life that doesn’t do this and the usual substances used to make hard parts of animals are silicates and calcium carbonate, among other rarer examples such as iron pyrite. Nonetheless, humans need phosphorus for that reason too, as do our close relatives. However, even the closely related sea urchins use calcium carbonate instead.
Hence several facts emerge from all this. One is that an apparently similar and more abundant element can’t necessarily be used for a similar function, assuming here that life can start from scratch. Another is that elements can get themselves into such a strongly bound state that it would take too much energy to use them for it to be worth it for life. A third is that life will sometimes substitute another element for the one it usually employs if it can. If a rare element is used, there’s usually a good reason for it.
Now the first problem with phosphorus is that it’s much more abundant inside a living thing than in its non-living environment, and the cycle that replenishes it is very slow. Phosphorus usually becomes available to the biosphere on land as a result of continental drift, the formation of mountains and erosion and weathering, and it’s lost to the land when it’s washed into rivers and the sea, where it disappears into sediment before becoming available again millions of years later. In the sea, it’s less of a problem but still a significant one because it’s only available to life as phosphates and it’s often found as phosphides instead. Ironically, there’s also an overabundance problem with phosphates in fertilisers being washed into bodies of water and leading to algal blooms, which can in fact be of cyanobacteria rather than algæ as such. Since some microörganisms can produce extremely powerful toxins, this can lead to massive marine die-offs and contaminated sea food. Where I live, a nearby reservoir was afflicted by an algal bloom and had to be closed off for quite some time, and this can also poison wildlife on land. These can also lead to high biochemical oxygen demand, which is where all the oxygen gets used up and the water becomes anoxic, which is incidentally a cause of mass extinctions, though on a much larger scale, in the oceans. This happens because phosphorus is relatively scarce and a significant limiting factor in how much life is possible in a given area, so a sudden influx of usable phosphate is likely to cause a chemical imbalance.
The Alchemist Discovering Phosphorus, Joseph Wright, 1771 and 1795.
This painting is thought to refer to the discovery of the element by Hennig Brand in 1669. Brand discovered it when searching for the Philosopher’s Stone, by heating boiled down urine and collecting the liquid which dripped off it. It turns out that this is actually quite an inefficient process and it’s possible to extract a lot more of the phosphorus by other means. The allotrope illustrated in the painting is unfortunately the highly toxic and dangerous white variety, so the alchemist is putting himself in peril by kneeling so close to the retort. The point to remember in all this is that phosphorus is found in urine, not in huge amounts but enough. This points towards a particular problem, highlighted by Isaac Asimov in his 1971 essay ‘Life’s Bottleneck’, which points out that humans “may be able to substitute nuclear power for coal, and plastics for wood, and yeast for meat, and friendliness for isolation—but for phosphorus there is neither substitute nor replacement”. Urine goes down the toilet and is flushed into the sewers, processed in sewage farms and the phosphorus from it ends up in the sea. It does gradually return to the land in biological ways. For instance, a seagull may die on land and her bones may become part of the terrestrial ecosystem, or she might just poo everywhere and return it that way, but the occasional gull or tern conking out in Bridlington is no compensation for millions of people flushing the loo several times a day. By doing this, we are gradually removing phosphorus from the land and returning it to the sea, whence it won’t return on the whole for millions of years.
Two ways round this suggest themselves. One is to eat more sea food. For a vegan, this is unfeasible and in any case fishing causes a lot of plastic pollution and is unsustainable, but of course it is possible to eat seaweed, and I do this. The other is not to allow urine into sewage in the first place or to process sewage differently. I have been in the habit of dumping urine in the garden, although I haven’t done this as much recently. It also contains potassium, and in particular fixed nitrogen, so in diluted form it is indeed useful for raising crops. However, this is on a small scale and a better system might be to process the sewage differently and put it on the land, being careful to ensure that harmful microbes and medication have been neutralised before doing so. Regarding seaweed, dulse, for example, is 3% of the RDI of phosphorus by dried weight, compared to the much lower amounts in most fish. Cuttlefish is the highest marine animal source. Human urine averages 0.035%, so you’d have to eat a lot of seaweed. However, in isolation, if you don’t, there will be a constant loss of phosphorus to the land. Guano is one solution, but not ideal and only slowly renewable.
The other problem with phosphorus follows from the same scarcity and the same use in living systems, but is more cosmic in scale, and I personally find it more worrying: phosphorus is rare on a cosmic level. In a way, all atomic matter is rare in this sense because the Universe is, as the otherwise really annoying Nick Land once said, “a good try at nothing” (apparently nobody has ever quoted that before, so that’s a first!). The cosmic abundance of the different elements looks like this:
The Y axis is a logarithmic scale, so for instance hydrogen is about ten times as abundant as helium and even in terms of mass is more common than any other element except helium. One notable thing about this graph other than the clear rapid decline in abundance with atomic number (the X axis) is that it zig-zags because even-numbered elements are more frequently found than their odd-numbered neighbours. This is because many elements are formed by the collision of α particles, which consist of two protons and two neutrons. Phosphorus is flanked by Silicon and Sulphur on here, though it isn’t specifically marked, and its atomic number is fifteen, i.e. an odd number. Chlorine, which is quite common in living things because it’s part of salt, is less common still.
Elements are formed in various ways, and this relates to how common they are. The Big Bang led to the formation of mainly hydrogen and helium a few minutes later, as soon as the Universe was cool enough to allow their nuclei to hold together and their nucleons to form, although they would’ve been ionised for quite some time rather than being actual atoms. Small amounts of lithium and beryllium formed in the same way, and if the graph is anything to go by this looks like it might’ve been the main way beryllium in particular formed. Then the stars formed and the pressure inside them led to helium nuclei in particular being pushed together to form heavier elements. The crucial step in this phase is the formation of calcium when three helium nuclei collide. Then, a number of other things happen. The star may end up going supernova and scattering its heavier elements through the local galactic neighbourhood. It may also form new elements in the process of exploding through radiation. This was until fairly recently thought to be the main means heavier elements were formed, but another way has recently been discovered. When a star not quite massive enough to become a black hole collapses, it forms into what is effectively a giant atomic nucleus the size of a city known as a neutron star. When these collide, they kind of “splat” into lots of droplets. Neutrons are only stable within atomic nuclei. Outside them they last about a quarter of an hour before breaking down, and they often become protons in doing so. This means that many of the neutronium droplets form into heavier elements, which are then pushed away by an unimaginably powerful neutrino burst from the neutron stars and again scattered into the galactic neighbourhood. Two elements, beryllium and boron, are mainly formed by cosmic rays splitting heavier atoms. Some, particularly transition metals such as chromium and manganese, formed in white dwarf stars which then exploded, and technetium along with all the heaviest elements, have been generated by human activity.
At first, the abundance of phosphorus didn’t seem to be a big problem. However, after studying supernova remnants, scientists at Cardiff University seem to have found that there is a lot less produced in supernova than had been previously thought. This means that phosphorus is likely only to be as common as it is here in this solar system in star systems which formed near the right kind of supernova to generate it in relatively large amounts. Couple this with the essential function of phosphorus in DNA, RNA, membranes and ATP, particularly the last, and it seems to mean that at this point in the history of the Universe, life as is well-known on Earth is likely only to be found in initially localised areas, surrounded by vast tracts of lifeless space. The systems containing life would gradually separate and spread out through the Galaxy due to the migration of the stars as they orbit the centre of the Milky Way, but they would remain fairly sparse. However, as time goes by and the Universe ages, there will be more such supernovæ and phosphorus will slowly become more common, making our kind of life increasingly likely. If life always does depend on phosphorus, we may simply be unusually early in the history of the Universe, and in many æons time there will be much more life. This possible limitation may have another consequence. We may be living in a star system isolated from others which are higher than average in phosphorus, meaning that to exist as biological beings with a viable ecosystem around us elsewhere, we would either have to take enough phosphorus with us or make our own, and even the several light years between stars which we already find intimidating is dwarfed by the distances between phosphorus-rich systems in the Galaxy, which may once have been near us but no longer are, and not only do we have to schlep ourselves across the void, but also we have to take a massive load of phosphorus with us wherever we go.
But that is biological life as we know it. A couple of other thoughts occur. One is that there could conceivably be life as we don’t know it. This doesn’t work as well if the substitution of phosphorus is the main difference, because if that could happen, it presumably would’ve happened with us, and it didn’t, because other elements with similar functions would’ve worked better if they were more abundant and out-competed with the life which actually did arise unless there’s something about this planet which does something else like lock the possible other options away chemically or something. However, there could just be drastically different life, based perhaps on plasma instead of solid and liquid matter on planets and moons, which has no need for phosphorus or even chemistry, on nuclear reactions taking place between nucleons on the surface of a neutron star as suggested by Robert L Forward’s SF book ‘Dragon’s Egg’, or even nuclear pasta inside neutron stars. Maybe it isn’t that life is rare in the Universe, but that life as we know it is, partly because it needs to use phosphorus.
There is another possibility. We are these flimsy wet things crawling about a planet somewhere in the Galaxy, but we’ve also made machines. In our own history, we are the results of genes, and perhaps also mitochondria and flagella, concealing themselves inside cells and proceeding to build, through evolution, relatively vast multicellular machines to protect themselves. Maybe history is about to repeat itself and we are going to build our own successors, or perhaps symbionts, in the form of AI spacecraft which go out into the Universe and reproduce. Perhaps machine life is common in the Galaxy and we’re just the precursors. There is an obvious problem with this though, mentioned a long time ago: what’s to stop swarms of self-replicating interstellar probes from dismantling planets and moons and making trillions of copies of themselves? If this arises through a mutated bug in their software, it would be to their advantage, and they could be expected to be by far the most widespread “life” in the Universe. Yet this doesn’t seem to have happened. If it hasn’t, maybe the beings which built these machines never existed either. Or maybe they’re just more responsible than we are.
This is not either/or, incidentally. We might theoretically be neither embarrassing nor boring or we might be both. Also, when I say “embarrassing”, I might be better off saying something like “shameful” or “social pariahs”. Please bear with me.
This is the famous “pale blue dot” photograph taken by one of the Voyager spacecraft on Valentine’s Day 1990, at which point it was beyond the orbit of Neptune. There is a minute fleck in this picture which I thought at first was a bit of dust on the screen. I tend to make similar mistakes whenever I see this image. Nonetheless, the “ray” on the right hand side has a tiny dot in it, and that’s Earth. Carl Sagan, the popular science guy, once said the following of this picture:
From this distant vantage point, the Earth might not seem of any particular interest. But for us, it’s different. Consider again that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there–on a mote of dust suspended in a sunbeam.
Carl Sagan, ‘Pale Blue Dot’, (c) 1994.
This observation has a lot in common with Douglas Adams’s Total Perspective Vortex storyline from the Secondary Phase of ‘The Hitch-Hikers’ Guide To The Galaxy’, where he imagines a machine which drives people insane by showing them how insignificant they are in a vast Universe. This doesn’t succeed in Zaphod’s case, either because his ego is the size of the Universe or because he was actually in a simulated universe set up for his benefit, or strictly speaking his deficit.
The Fermi Paradox, which in case it’s somehow passed you by I will restate here, was voiced by the nuclear physicist Enrico Fermi in 1950, although Konstantin Tsiolkovskii had said something similar in 1933 and suggested the Zoo Hypothesis as a solution. Simply stated, it’s the apparent discrepancy between a Universe in which life is possible and the lack of evidence for the existence of aliens. That is, given that there is intelligent life on Earth, as is often claimed, and that Earth and the Sun are both quite unremarkable, why haven’t we had any contact with intelligent life forms from elsewhere in the Universe? Not only is there no apparent evidence today, but nor does there seem to have been any visitation from aliens at any time in the whole 4 600 million years since this planet formed. Since I’ve mentioned the Zoo Hypothesis, I should probably explain what that is. It’s the idea that we are known to aliens but they have chosen not to interfere with us, at least so far, so as to observe us as an interesting species.
This is actually the solution I favoured as a teenager. I liked the idea that there was a Galaxy teeming with intelligent life forms of various species out there with an ethic of non-interference, who were observing our species undetected. This is also very similar to the Prime Directive of the ‘Star Trek’ universe.
Right now, I have a much more depressing front runner as to the solution, although it’s not as much of a downer as the Great Filter, which now I’ve mentioned it I’ll have to outline, but later. At this moment, the most plausible explanation seems to me to be that phosphorus is relatively scarce. This argument goes as follows: non-carbon based life is unlikely because on this planet silicon is more abundant by far than carbon and yet there’s no silicon-based life here. Phosphorus is the rarest core element required for life as we know it, being incorporated in adenosine triphosphate and nucleic acids such as DNA, and it being so rare suggests that it wouldn’t be used unless there was no alternative. Then it turns out that phosphorus is even rare in our own solar system off-Earth. It’s ten times more concentrated in the human body than in the crust, and more than a thousand times as concentrated in the crust than in the matter of the solar system. Phosphorus only seems to form during a particular kind of supernova explosion, as opposed to within the star before it becomes a supernova and distribute the elements, meaning that phosphorus may only be at all common in certain parts of the Galaxy, and that also may prevent intelligent spacefaring civilisations from spreading far because they might have to take all their phosphorus with them or make it in situ. Moreover, it may be that as the Universe ages more phosphorus will accumulate and it will become more hospitable for life, which means we might just be really early.
I hope this is either not true or that another form of life dominates the Universe, such as plasma-based life living in nebulae or the depths of space between the stars. Nonetheless many other explanations have been offered, one of which is primarily interesting for the purposes of this blog post because of its origin: the Dark Forest.
There’s a famous and celebrated trilogy of SF novels by the Chinese author 刘慈欣 (Liu Cixin). I won’t go into the details of the plot, but the overarching idea in it is that the reason we haven’t heard from aliens is that the rational approach to the existence of extraterrestrial life is to regard it as a threat, and therefore that they’re all hiding due to the threat, and making oneself known, as we have if there’s anyone out there, is foolish and suicidal. More generally Liu Cixin believes that we project artificial positivity onto aliens, regarding them as more enlightened and benevolent than it’s reasonable to expect them to be, while simultaneously underestimating the benevolence of humans. I don’t agree with this at all as I think it’s based on how groups of human beings have behaved under patriarchy towards each other and there’s no reason to suppose aliens have the same characteristics and history as our highly contingent tendencies. However, one interesting aspect of the Dark Forest hypothesis, as it’s known, is that it’s an idea from fiction which has turned out to be taken seriously by theorists dealing with the real Fermi Paradox, and the same is true of the two main ideas I want to talk about today.
The first of these is that we’re embarrassing, and for this I’ll go back to Douglas Adams. In ‘Life, The Universe And Everything’, the (obvious spoilers) premise is that the reason aliens are always invading Earth is that they find the game of cricket to be in extreme bad taste due to a devastating war early in Galactic history. Taking this up and running with it, what if the reason we are not in contact with aliens is that there’s something about the way we are which does something like make us a cognitohazard to them, or that our behaviour or values are so reprehensible that we can’t be accepted in polite society? Maybe we are metaphorically wearing our underpants on our heads, or are like the racist uncle who can’t resist making off-colour jokes.
To state this more clearly, there are intelligent life forms elsewhere in the Universe, and they are aware of our existence. The reason they don’t make contact is that there is something about us they find abhorrent, not physically speaking but along the lines of our customs, culture, values or practices. They find us rude or to have crossed a line they would never dream of doing. Alternatively, they can’t contact us safely because our behaviour constitutes something which would infect their psyche and cause severe damage to their civilisation.
There’s a peculiar visual phenomenon which I’m going to suggest you don’t Google (will that verb be dated soon?) called the McCullough Effect (I’ve deliberately spelt this wrong). It’s hazardous to search for this online, and I have reason to suppose it might be more hazardous for me than the average person. It takes the form of two patches of black and white stripes, one set horizontal and the other vertical. If you look at them for a few minutes, black and white horizontal stripes look pink and black and white vertical stripes green, for a period of about three months. The idea isn’t new, but as far as I know this is the only real world example that’s been discovered so far which works on neurotypical people with good colour vision. My hypothesis here is that there is something about us as humans, or possibly our dominant culture, which has a similarly but possibly more severe harmful effect on aliens who come into contact with us, and therefore we have been quarantined to protect the rest of the Galaxy. If this is true, it isn’t clear to us what it is or whether it’s all-pervasive or permanent.
There’s a less morally-neutral version of this possibility. Maybe our selfishness and materialism have led to us being cast out of the Galactic community, but we aren’t permanently bound to it, and if we free ourselves from it as a species they may make contact. This sounds a little like the idea of the “Fall Of Man”, and one shouldn’t underestimate the role mythology or spirituality may play in causing this idea. Or, it could be something we just can’t guess at, as with Douglas Adams’s example that it’s because some humans play cricket. It could be something as arbitrary as that, which will never occur to us because it’s part of being human. Maybe we’re being shunned, in other words.
The other possibility is suggested by Iain M Banks’s story ‘State Of The Art’. Obviously I need to flag up spoilers here too, but I also need to get on. In this novella, a post-scarcity civilisation called the Culture surreptitiously visits Earth in 1977 and decides that it’s so average that it’s not worth making contact with us. I didn’t get this from the story myself but apparently that’s how most people read it.
To state this more clearly, the solution to the Fermi Paradox is this. We are in a vast and life-rich Galaxy, with plenty of advanced technological civilisations, and we just aren’t that interesting. It isn’t that there’s anything particularly wrong with us or that we’re being studied as the Zoo Hypothesis has it, just that we’re really boring and ordinary. In this scenario, there could be numerous planet-bound civilisations like ours which are also wondering where all the aliens are, but the advanced aliens have all been there and done that, and don’t have much interest in a history of a typical primitive but intelligent species living in a boring old ordinary solar system. We’re simply “Mostly Harmless”, to get back to H2G2. The scale of the Galaxy is such that paying any attention to us would be like getting fixated on a bit of mouldy bread accidentally dropped behind something in the kitchen, which might be interesting to a mycologist but unless it really starts to stink or something, they’re not going to pay much attention to it/us.
This explanation has the merit of according with what we already know about our apparent place in the Universe. We’re on a pale blue dot lost in the vastness of the Cosmos. I had to peer at that picture for a while before it registered with me that Earth wasn’t a random fleck of lint or a bit of dandruff. It is feasible that some kind of survey of the Galaxy could have been undertaken which picked us up, but it’s like a huge shoal of fish. There’s a species of fish called the Lanternfish. Actually there isn’t. There are more than thirty genera of this fish, and it’s a good illustration of my point that I didn’t even know that. The remarkable thing about lanternfish is that they are so numerous that there may be up to sixteen billion tonnes of them in the ocean and they may be the most populous vertebrate in the world. They live in the middle depths of the ocean throughour the world, and in that sense they are important. Their average weight is 250 milligrammes, so a low estimate of their global population is a million times that of the total population of humans in the world. But have we heard of them? Do we think much about them? They’re also one of the most diverse families of fish in terms of number of species, but this still doesn’t really matter to anyone apart fom a few specialist experts. Now consider a single lanternfish. Being a living being, of course it’s important and I’m not about to suggest that I consider it disposable or not worth keeping alive, but to the average person, who is going to care about or even think about such a fish? Maybe this is what the planet Earth and its human population is like to the Galactic community. There is maybe someone in an alien university thousands of light years away who has considered our civilisation as part of their PhD thesis, as a footnote somewhere in a book nobody will ever read, or whatever the alien equivalent of that is, but even that’s a pretty long shot. The sheer scale of the Galaxy supports this idea.
Both of these suggestions have in common that the question “where are all the aliens?” is kind of inverted. It’s more like the Biblical quote “Who is man that Thou art mindful of him?” Maybe the real question is why we would consider ourselves worthy of attention. On Earth, we are a big deal, a big fish in a small pond, but in the Galaxy perhaps we’ve either mistaken a fireplace for a urinal in the home of a prospective in-law or we’re like an individual lanternfish swimming a kilometre down in the Southern Ocean and nobody has any reason to care.
Triton, along with the similarly-named Titan and also Ganymede, is one of the largest moons of the outer system. Before Voyager 2 reached it, it was considered possibly the largest moon of all. Moreover, apart from our own highly anomalous Cynthia, it’s large in proportion to its planet’s size. Using the largest moons of each planet, the proportions of their masses work out thus:
Just for reference, the ratios for Pluto:Charon are 1.96 for diameter and 8.22 for mass, but Pluto‘s status as a planet is not unquestioned. It can in any case be seen that of all the large moons, Neptune’s Triton is still in proportion and there’s a big gap before our own special case, but it is still unusually big.
A common mechanism for the formation of moons is for the region around a planet to behave like the solar nebula did when the planets themselves were formed, with eddies in the cloud pulling in matter as the planet takes shape. Hamlet’s moons may be an exception to this, as they may result from the trauma that planet underwent. Outer and irregular moons are, however, often the result of captures and this is particularly evident when they orbit the opposite way from most Solar System bodies, and Triton is by far the largest body to do this. This has been known since its orbit was plotted in the nineteenth century. Due to its size and therefore relative brightness, the moon also holds the record for the shortest gap between the discovery of its planet and its own, as it was found in October 1846 CE, only a month after Neptune. This, however, is not as impressive as it sounds because all the planets out to Saturn have been known since ancient times and Pluto is very small and may not be counted as a planet, so it basically means that of the two planets discovered in the telescopic age, one of them has a very large and relatively bright moon which was easy to spot.
Certainly by the ’70s, Triton was, as it still is, considered to be a captured planet, though that would probably generally be qualified as “dwarf” now. Given the controversy of what counts as a planet, Triton of all worlds in the system has surely got to be the closest to that definition, as although it may have undergone the mishap, if that’s an appropriate word, of being grabbed by Neptune, it’s quite large and massive and probably used to dominate its orbit, as the 2006 IAU definition demands. Strictly speaking, and perhaps by being a bit arsy, Earth doesn’t even count as a planet by that definition. Hear ye then: Triton is a planet. I was first introduced to this piece of information in the ’70s, which is how I can make that provisional estimate of its timing, and consequently looked forward to the Voyager missions as including an encounter with a body likely to be very like Pluto. At the time there was little prospect of a mission to that planet, so it was the best I felt I could hope for.
The Voyagers took advantage of a rare planetary alignment which only occurs once every two centuries and started in 1976, dubbed the “Grand Tour”, which would allow probes to visit several planets in a row. This idea dates from at the latest 1971, and there were initially three possibilities. Two involved Jupiter, Saturn and Pluto and the other all the gas giants, but it was impossible to visit both them and Pluto on the same mission, at least efficiently enough to be practical. The ultimate decision was to take the last option, although Voyager 1 is a bit like the first two with the omission of Pluto. Also, although the Voyager 2 mission resembles the final option quite closely, it isn’t actually the same as the initial plan, which involved launching in 1979, visiting Jupiter and Saturn in ’81 and ’82 respectively, Hamlet in ’86 and Neptune in ’88, as the Voyagers were launched in ’77. The earliest option for Pluto inolved a ’76 launch, visits to the two inner gas giants in ’78 and ’79 respectively and Pluto in ’85. Although the final choice was, I think, a good one, it’s interesting to contemplate what might have been. It would be disappointing not to have visited the ice giants but amazing to have got to Pluto so early, and it also seems very likely that if that had happened, Pluto would never have been demoted. However, it was not to be, and this makes Triton a kind of Pluto substitute. It is in fact very likely to be similar to Pluto and it’s worth comparing the two.
Excluding the Sun, Triton is the fifteenth largest body in the system, Pluto the sixteenth. Eris is next on the list, incidentally. In terms of mass, Eris is between Pluto and the more massive Triton. Circling Neptune, Triton takes 165 years to orbit the Sun , Pluto 248, which is close to a 3:2 ratio (lots of ratios in this post for some reason) like the other plutinos. Considering its similarity, it seems likely that Triton was itself a plutino with a 248-year period like Pluto’s (which is what defines them), and right now I’m also wondering whether some of the other moons of Neptune, particularly Nereid with its peculiar orbit, were in fact originally moons of Triton. I expect this has already been researched.
Being retrograde is not the only peculiar feature of Triton’s orbit. It also varies its tilt through a cycle corresponding to only four Neptunian years, and is moreover remarkably round, by contrast with Nereid’s. Its distance from the barycentre (centre of gravity between two bodies) varies by less than six kilometres each way. This may be the roundest orbit in the Solar System and is quite remarkable. Our own orbital eccentricity is a thousand times greater. Hence there are a few combined mysteries here, which are probably related: the moon orbits backwards, shifts rapidly (over a period of about five centuries) in how tilted its orbit is and hardly varies at all from its mean distance of 354 759 kilometres from the barycentre, which is around seventy-five kilometres from the centre of Neptune. The size of the orbit is also only a little less than Cynthia’s around Earth. I have an illustration by Luděk Pešek of the moon in Neptune’s sky, painted in the early ’70s, and at the time it was considered much larger than Cynthia. It’s now been found to be somewhat smaller at 2706 kilometres diameter, and is of course somewhat less dense due to its ice content, although Cynthia, being formed from the Earth’s outer and lighter layers, is only about 50% denser. That said, Triton still averages over twice the density of water, making it one of the densest objects in the system beyond the orbit of Jupiter, and also denser than Pluto. Given the nature of its surface, this is all the more remarkable, and I’ll come to that.
Before its capture, Triton would’ve dominated its region of the system beyond Neptune, and perhaps even have counted as a planet in its own right by the IAU 2006 definition. Neptune is in a peculiar position regarding the Bone-Titius Series, and if that is in fact a law of nature it could be expected to have been somewhere else in the past. This would presumably in turn have meant that the plutinos have fallen into orbital resonance with it since it moved and the presence of small, solid planets beyond its orbit would lend the Solar System a pleasing symmetry, with small rocky planets in the inner system, gas giants in the middle and a further succession of small icy planets beyond them. It is of course highly speculative to suggest that Neptune used to be somewhere else. Olaf Stapledon supposed Neptune to be followed by a further three planets, of which Pluto was extremely dense and made of iron, because only with such a hefty planet would be able to perturb Neptune to the extent it is. It was common at the time for scientists to presume this as they’d predicted Pluto’s existence from these perturbations, but I’ve gone on about this elsewhere.
Pluto and Triton are almost the same in composition, suggesting a common origin. The moon’s surface, however, is somewhat different. It’s unusually flat, with variations in elevation of less than a kilometre. It also has a surprising composition: it’s made of frozen nitrogen. At this distance from the Sun, the gas which makes up most of our atmosphere composes the solid, though also soft, surface of a world. It’s therefore no surprise that the surface temperature is exceedingly low at -235°C. However, there is also a greenhouse effect, in this case considerably more literal than usual. The nitrogen forms a clear surface which traps the sunlight just below it, heating the subterranean nitrogen and causing it to erupt out of the surface like geysers or volcanoes to a height of around eight kilometres. This then drifts downwind by as much as a hundred kilometres, leaving streaks on the landscape. This process also maintains the moon’s nitrogen atmosphere, which is thin by terrestrial standards but not as tenuous as many of the atmospheres of other moons, at fourteen microbars. Although this may not sound like much, it’s enough to be a collisional atmosphere. That is, the molecules in Triton’s atmosphere are near enough to one another to come in contact at least occasionally, which means the air behaves as a fluid like air at sea level on Earth, rather than just bouncing around or orbiting the moon as it does on our own. Even so, Triton’s atmosphere is a lot thinner than expected. The lower the temperature, the easier it is for a body to hold on to gases and perhaps liquids if the atmospheric pressure supports them. Nonetheless, Triton doesn’t seem to be very good at it. Its surface gravity is 0.0794 that of ours, over half that of Titan, whose atmosphere is several times denser than Earth’s and whose temperature is something like two and a half times higher. There’s a small amount of methane in the atmosphere too, making it like a much thinner version of Titan’s, but also colder since it’s below both substance’s freezing points. Just as an aside, it’s been conjectured that of all the substances likely to form oceans on planets or moons somewhat similar to Earth, i.e. oceans on the surface along with land masses or islands, nitrogen would actually be the most common liquid of all, with water only coming in second. Triton is not a world with permanent bodies of liquid on its surface, but like Cynthia, it does have large flat plains of solidified “lava”, in this case frozen nitrogen, which contributes to its general flatness. Unlike water, most liquids freeze “under” rather than “over”, so the frozen nitrogen lava plains of Triton would have done so by cooling on the surface and then precipitating down inside the body of liquid, gradually filling up until the whole lake or sea was frozen solid, except that it would then have melted and vaporised in some places and pushed through once again. The geysers are near the south pole, similar to the Enceladus situation, but this is a much larger and heavier world than that moon. However, there are also claims that the lava is in fact an ammonia-water mixture, so all of this is provisional. The fact remains that most of the atmosphere is nitrogen.
The resolution of the picture at the top of this post is surprisingly large considering it’s a mosaic of images captured by a camera from the mid-’70s. Although it’s diminutive on this page,clicking on it will show it in its full glory. Pixels are only five hundred metres across at the centre, so this is a pretty detailed map of most of the surface and would show medium-sized parks if it were a picture of Earth. It’s like a photo of Earth from the ISS, although of course the whole of our planet wouldn’t be visible from such a distance. A distinctive feature is the so-called “canteloupe terrain” because it looks a bit like this kind of melon:
Triton’s version looks like this:
The winding heights are several hundred metres high and a few hundred kilometres across, and the plains they surround are safely two hundred kilometres wide, which is significant for a moon which, though large, is only about ten times that in diameter. The ridges consist of water ice which has been squeezed upward, and the whole surface of the moon is quite young as it has few craters. It could even be Cenozoic. This is possibly a surface which didn’t exist when T. rex walked the earth, although another surface did. To my mind, this raises the question of whether Triton was actually an independent planet at the time and if this melting can be blamed on the capture.
The similarity of the smooth basins to lunar maria will not have escaped you. The difference is that whereas those are made of basalt, these are nitrogen, as I’ve said. It’s worth bringing up again though, because on different worlds at different temperatures the same kinds of processes and structures exist but are made of different substances. On the whole, most substances which can be solid, liquid or gaseous in a given situation without major changes are, unsurprisingly, broadly subject to the same kinds of physical laws. The exception, more surprisingly, is water, because in the state with which we’re familiar, that is, under enough pressure to give it a liquid phase but only enough to ensure it has the most loosely spaced solid one, it expands and therefore floats when it freezes. This would have consequences such as the canteloupe terrain on Triton, which could be caused by its expansion as it solidified. Ironically, liquid nitrogen and molten rock (a bit of a generalisation) have things in common which they don’t share with water, a highly anomalous substance, due to water’s expansion on cooling and surface tension, among other things.
The solid nitrogen on Triton can be seen as the slightly blue-green streak across the image at the top of this post. It’s actually β nitrogen, which forms hexagonal crystals although they don’t form arrays like graphite or honeycomb. I can’t swear to this, but since the element immediately below nitrogen in the periodic table is phosphorus, whose least derived form is the dangerous but waxy white phosphorus, and I suspect that solid nitrogen fairly close to its triple (“melting”) point is also like this. This is not a thorough scientific appraisal so much as a hunch. White phosphorus slowly combines with oxygen in Earth’s atmosphere, and nitrogen as such is highly reactive, hence its use in explosives, but generally reacts with itself to form a highly inert gas at temperatures compatible with human life. On Triton, whether or not it’s reactive it may not have much to react with and the lower temperature would inhibit many such reactions. The issue here is really that although, as I’ve said, in some circumstances it hardly matters whether the substance in question is silica or nitrogen, as both can form volcanoes, erupt, produce lava flows and the like, such a substance as solid nitrogen or a mass of liquid methane on a lake on Titan is far from our own experience and our expectations can be misleading. However, it does seem highly feasible that the plains of the canteloupe terrain and the general flatness of the landscape is due to the waxy softness of the nitrogen which forms part of them. At this temperature also, water ice is almost a normal solid, expanding with increasing temperature and contracting as it cools, but it has clearly passed through the anomalous phase we think of as normal behaviour for a liquid.
What’s Triton’s interior like? Nitrogen in this solid form is very slightly denser than water at our freezing point, so it unsurprisingly covers the surface and forms a substantial part of the crust. The moon is rockier than the other moons trans the asteroid belt with the exception of Io and Europa, which are basically just balls of rock like the inner planets with a thin coating of other substances. Triton does still have an icy mantle but it will have a rocky core high in metals like a terrestrial planet’s. The brightness of the nitrogen surface cools the moon while simultaneously heating the upper layers of the crust, making it one of the coldest worlds in the known Solar System. The geysers are driven by the heat of the Sun, such as it is, emphasising what looks to us from here, close in to the Sun, to be a thermally delicate state. It might be expected not to last long in its present form when the Sun becomes a red giant, but the same is true of Earth. Solid and liquid matter as such is not the kind of thing which can cope well with the kind of temperatures found near stars. There’s also the “logarithmic” effect of low temperatures. The freezing point of water is about half the temperature of a hot oven and its boiling point at sea level is less than twice the temperature at our South Pole in midwinter. Nitrogen and oxygen have similar melting and boiling points at the rather mind-boggling sea level atmospheric pressure, and to us the fourteen degrees of difference between the boiling and freezing points of nitrogen sounds very narrow, but if centigrade had been standardised with nitrogen instead of water, absolute zero would be -550 degrees below zero. There’s an effectively infinite range of temperature before reaching absolute zero, which is like the speed of light in that respect – effectively inaccessible and some kind of ultimate limit.
Although they have their own smaller moons, Pluto and Charon are effectively a double planet system. It’s been theorised that the same was also true of Triton before its capture. Many other Kuiper belt objects are binary, and modelling of the dynamics of capture show that Triton is more likely to survive if this was so. The other object would be ejected from the system. To my mind, this contrasts with Hamlet’s situation, where a similar collision may have resulted in the “moon”, such as it was, being incorporated with the substance of the planet itself and also disrupting its axial tilt. The question then arises of where Triton’s companion might be now if it survived the encounter, and in my current ignorance I wonder about the similarly-sized Eris.
The name Triton originates from Poseidon’s (i.e. Neptune the god’s Greek counterpart) son, and has been more widely used for other purposes than most other names of major planets and moons. For instance, this is a triton:
This is the animal that first springs to mind for me when I think of newts, but they are nonetheless known as tritons. It’s also used as the name of a sea snail and a species of cockatoo. The list is much longer than for many or most other names also used for celestial bodies, which seems rather anomalous to me and possibly reflects the relative obscurity of the moon compared to some others, though maybe I’m out of touch in saying that.
Neptune’s satellite system as a whole is sparser than the other gas giants’, with only fourteen known moons. Until the ’80s, only two were known. This may be connected to Triton’s presence, either enabling it to remain without disturbance or maybe due to its own disturbance of the system. When Triton first arrived, its surface is likely to have been molten for an æon. In Triton’s case this presumably means a liquid nitrogen ocean over a water ice bed, which makes it seem that it was captured in the late cryptozoic eon, if that estimate is at all accurate. Hence over the period when Earth was almost frozen over itself and had little or no surface liquid, Titan and Triton both had oceans, and the latter would’ve been a possible member of the very large number of worlds with liquid nitrogen bodies of liquid on their surfaces, which is plausible but unknown. It’s also unclear whether it had landmasses. But in any case, the number of moons is surprisingly small. The comparably-sized Hamlet has more than two dozen, but Neptune only has fourteen. All but two of these were unknown before Voyager. Triton’s mass is two hundred times the mass of all the other moons put together.
As a world, Triton is somewhat smaller than Cynthia. Its surface area is 23 million square kilometres, 40% of which has been imaged. This makes it bigger than any country and a little larger than North America, but smaller than Afrika or Eurasia. It seems entirely feasible, probable in fact, that its surface is covered by more nitrogen than is present in our own atmosphere. Triton and Pluto both have irregular pits with cliff edges on their surfaces which are not craters, called “cavi”. Ten of these have been named, all after water spirits. Cavi usually occur in groups. There are only nine named craters. Other features include those found elsewhere on other solid bodies in the system (and probably throughout the Universe): dorsa, sulci, catenæ (chains of craters caused by meteoroids breaking up before impact), maculæ (dark spots), pateræ (irregular craters, not the same as cavi), planitiæ and plana. There are also “regions”.
Tholins are present on Triton, where they are distinctive in containing heterocyclic nitrogen compounds. This makes them chemically similar to alkaloids, which are a family-resemblance defined class of nitrogenous compounds which tend to have rings containing nitrogen in their molecules, a markèd physiological effect on some organisms and originate in plants. However, there are animal alkaloids such as toad poisons and adrenalin, so it’s entirely feasible that there are basically drugs on Triton’s surface. Unlike Titan, there are no persistent solvents on Triton, so in a similar way to moondust being chemically different from matter in a wet or oxygen-rich environment, Tritonian tholins might be quite reactive on Earth, and might in fact be explosive. All this is my speculation, but I stand by it and feel quite confident that it would be so.
To conclude, then, probably less is known about Triton than any other body of comparable size in the system up to and including Pluto. It’s only been visited once, by Voyager 2, and was in fact the last world to be encountered by it before the “void”. Nonetheless, it’s an important world and has probably the best claim to planethood of any moon. The behaviour of objects in the outer Solar System at this point reminds me of snooker.
Next time, the other moons of Neptune, which are also interesting but even less well-known.
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.
A Box Of Chocolates 