A few years ago on this blog, I went through every episode in the Original Series of Star Trek and reviewed them all. Well, I say that. One of the posts was actually a short story told from Uhura’s point of view as she sat around on the bridge with decidedly relaxed hair not doing much while the rest of the bridge crew beamed down to the planet, but leaving that aside I did review every episode, and I also did the animated series and TNG as a whole. If you’re interested, the reviews start here.
Now it’s occurred to me that I have now written a few posts on the subject of various bodies in this Solar System, not very systematically and partly because a Generative Adversarial Network (GAN) suggested them to me. I am going to ramble just a little bit in this post, so I’ll go off on a tangent here and talk about what a GAN is.
A GAN is a pair of neural networks used in Artificial Intelligence (AI) which competes against itself to produce better results. What’s a neural network then? Well, to some extent we are, although not entirely, and there’s some controversy as to how much a human being’s essence could be captured using such a structure. Most of the time, the term “neural network” doesn’t refer to a biological entity like a human being or a nematode worm, but to a simulated structure being run in software which attempts to mimic the function of a real such network. It has an input layer consisting of sensors, for example, one or more hidden layers, where the signals from the sensors are combined and acted upon, and an output layer, often in the form of a visual, textual or auditory representation. The retina is an example of a neural network, and starts to process the visual input to the eye before presenting it to the brain. For instance, rod cells are more sensitive than cone cells and several of their inputs are combined by a neuron-based inclusive-or gate such that a single stimulated cell will set off the neuron, enabling one to see better in low light, whereas the cone cells are in one to one correspondents to the neurons, enabling higher resolution vision in colour in good light conditions. Individual nodes in an artificial neural network can be made more or less sensitive according to their “experiences”, so they can be gradually trained. This technique is used in a GAN. These pit two neural networks against each other. An individual network can learn, for example, to recognise a face by being shown thousands of pictures of faces and producing ratings as to how face-like it judges the input to be, which is then judged by the human programmer, allowing it gradually to get better at recognising them. This human programmer can be removed and replaced by a software training judge, which allows the process to occur much more quickly. GANs focus on the weaknesses. For instance, they might be good at recognising pairs of eyes but not mouths, so if the eye recognition is good enough, the other part of the program will concentrate on making it better at knowing what a mouth looks like. I haven’t described this particularly well, but GANs are basically artificial intelligence which is able to recognise and predict, and even make, particularly good patterns. Faces for example:
GANs and other AI can be really dodgy because if you train them on the wrong source material they can end up freezing previously human prejudices into the software. For instance, a GAN trained on job applications may start reproducing the sexism and racism of the recruiters and a GAN trained on mainly White human faces and those of other primates has ended up classifying Black faces as those of gorillas. It’s therefore both far from perfect and potentially insidiously harmful, because nobody knows exactly how they function.
I have referred previously to my use of GANs on here to work out what this blog is actually about. In case you don’t already know, it’s called ‘A Box Of Chocolates’ because you never know what you’re going to get, and nor do I. In fact, it’s possible that an outsider would be better at recognising what a typical Nineteenthly post would be about and look like than I would, because I’m not aware of my prejudices and style, but other people probably are. I do have some self-awareness but I don’t know how much, which raises the question of how well we can really know ourselves.
All of that notwithstanding, I do sometimes use GANs to inspire blog posts. It would make a lot of sense to do this with popular titles written by others, but I suspect this would have two adverse effects. It would restrict subject matter to the more “commercial” and popular subjects,and it would make them clickbaity, which is very irritating. We already get exposed to too much stuff which is inside our reality tunnels and I don’t want to make this any worse. On the other hand, I know I’m unconsciously eccentric and therefore the things I go on about and the ways I react are unusual. For instance, I once surprised someone in a discussion about the legalisation of hard drugs by saying that a single parent in a deprived area might fear the effect of the decriminalisation of hard drugs on her children because it might stop her from selling them and supporting her family. This is apparently an unusual juxtaposition of ideas. However, the kind of ideas I have might still be detectable by a GAN.
In a remarkable turn of events, I began the next paragraph with a cliché (maybe not so remarkable after all), so I am subject to talking about “normal” stuff from time to time. Even so, I do use this technique and it’s almost a form of divination, like looking at tea leaves or dropping molten lead into water and interpreting the shapes, because the text results often read as if they’re referring to events and preoccupations in my life which clearly the machine can know nothing about. Or can it? There’s a famous case of a teenager who got mailed vouchers for baby stuff because the AI interpreting her shopping habits, which were not obviously anything to do with being pregnant, was able to predict that she was going to have a baby soon. She hadn’t told her parents, so this is how they found out. It’s conceivable (geddit?) that someone might not know they’re pregnant before the computers do, and likewise software might be able to deduce facts about oneself which one is perhaps repressing or doesn’t even know. This is often useful, as with the CASCAID career software, which has for at least forty years been suggesting careers to schoolchildren and others. At the same time, we see patterns which aren’t really there, and with the psychotherapist program ELISA for example, it really feels like one is talking to a counsellor and it can even be useful.
In a remarkable turn of events, as mentioned here I submitted some recent blog titles and was rather surprised to find that rather than suggesting more possible subjects, the GAN began to type out what looked very much like a blog post about Titan, hence my actual production of the last post. Most of the AI-generated text didn’t make much sense. For instance, it mentioned a crater being in orbit above the moon. However, some of it really did, and the general topic of the text was the possibility of humans settling on Titan and exploiting it for economic benefit, which I ended up mentioning in the real post.
Another possible use for the GAN, apart from actually getting it to write articles which would at the moment mainly be gibberish – they would appear to make sense and use grammatical sentences with English words in them, but the whole post would be nonsense – is to submit tags which are popular in order for it to generate more. I’ve also done this and it works quite well. Incidentally, if you put in this paragraph, this is one result:
ussion/comments/29d2w3/why_are_there_exceptions_to_the_guests_and_ancillary_suggestion_to_add/ You can read that at the end, too. The idea here: a link to another subreddit which mentions the use of "GAN" - is just a joke.
The article at the top is a bit hard - it includes this tag, but no one has heard of it. It seems that many people actually prefer to keep it unimportant. Here it is, in the final form of this post:
For a comment on this post here is a screenshot of what we have just submitted: http://redd.it/29d2w7/reddit_posts/3
For an argument with the question here is about the link to this reddit, which is not worth mentioning.
I used the following for this
Not very useful!
After that digression then, here is my immediate plan. I’ve found myself covering various planets, moons and other bodies on this blog, but one thing I’ve never done is a systematic survey of the individual aspects of the entire Solar System. I’ve mentioned Mercury, Venus, Mars, Titan, Uranus, Neptune and Pluto but none of the moons or asteroids, or the general layout of the system, which is quite germane. However, if I did this incessantly like I did with ‘Star Trek’, the reader would be subjected to day after day of posts on various worlds, so although this forms part of my plan I also want to intersperse it with other topics. Otherwise, you will “know what you’re gonna get” – yet another post on a planet. It also means you can skip it if you find it boring.
Now is also a good time to say something about my attitude to astronomy.
It’s really easy with astronomy to slip into a mindset that it’s something that’s just “out there” with no connection to everyday life. This is a problem I used to have with the science workshops when I was more directly involved in home education. In general, physics, chemistry and biology lend themselves really easily to activities and learning for a group of children who turn up during the day. However, children also have bedtimes and in this country it doesn’t get completely dark in the middle of the summer, so for astronomy there isn’t much “hands on” activity for groups. The Sun and Cynthia (“the Moon”) are available and you might get lucky and witness a transit of Venus, but beyond that there’s precious little. Hence if you’re not careful you end up dealing with astronomy at arm’s length, as it were. It isn’t helped by the fact that a lot of space stuff is associated with planetary romance, space opera and science fiction, which further removes you from the real subject matter. It introduces all sorts of preconceptions about space, such as the idea that the asteroid belt is a hazardous zone strewn with dangerous spinning rocks or that space is like a two-dimensional ocean. There’s a place for all that of course, but I want to really feel space in all its gritty reality. One of the Apollo astronauts was asked about what colour the lunar surface was, and he replied that if he wanted to see something which was the same colour he’d go out and look at his concrete driveway. There’s something really mundane about this, and whereas it makes it sound boring it also provides a real link between everyday experience and astronomy which can be hard to come by.
This, then, is my plan. I will be blogging about various worlds in our Solar System and about the Solar System as a whole, interspersed with posts on other subjects, and I aim to do it in such a way that it won’t seem to be abstract or “out there” but as real as going down the street to the chemist. We all know in the abstract that we’re in space and live on a small blue dot lost in the vastness of the Cosmos, but we also spend a lot of time thinking of ourselves as like the filling in a sandwich with a black colander on top of it. There are good practical reasons for not thinking of the world like this, such as the constant awareness of the limited nature of Earth’s resources, the unity of the planet and the preciousness of this tiny oasis. It also seems in order to be aware that the other worlds around us are also whole worlds, as much as Earth is, and recognise what might be special about our Solar System compared to others, and what’s typical.
At some point maybe about forty years ago it was noted that there were thirty-three moons in the Solar System plus nine planets, and in addition to those there are the centaurs, asteroids, smaller moons, comets and Kuiper Belt objects. Nowadays many more moons are known than that number in either the Jovian or Saturnian systems alone. Hence there is ample material for this kind of thing, and also ample material to be boring with. One thing I want to emphasise is that because so far as we know this is the only world with life on it, I want to approach the celestial bodies on their own terms, not just as potential places for humans to settle on or where life might or might not exist. The Universe is not just about life. That said, I will also be considering this aspect, along with what humans have had to do with them because otherwise there’s a risk of making it too disconnected with what we know.
On a personal note, I’m somewhat impaired due to the fact that I live in a cloudy part of this planet, have poor eyesight and am not blessed with dark skies, although this may change. People with good vision may not appreciate the problem with looking at the night sky when you’re short-sighted. Stars, with the Sun’s exception, are of course very dim compared to what we generally see during the day. I have the choice of looking at the sky with glasses or without. With the latter, the light of a given star is very blurred and diffuse, to the extent that I don’t think I can even see second magnitude stars such as Algol or Polaris. With the former, the material from which the lenses are made cuts out much of the light before it even reaches my cornea. Therefore my only option is to use a telescope or binoculars. I used to share a reflector with my brother, but unfortunately lost some vital bits of it in the back of someone else’s car, so that was that really. All of this leads to exactly the kind of disconnection I want to avoid with the rest of the Universe. I think this may have led to me over-compensating for my disability, to surreptitiously quote Mr Adams for the second time in three paragraphs, and I feel a more urgent pressure perhaps than most to make this connection.
Quick summary then. Our Solar System currently probably extends at least a light year and a half in each direction from the Sun. Beyond that point, the gravitational pulls of other stars become significant and an object can’t be said to be orbiting it. As the Sun moves through the Galaxy in its orbit, which lasts 200-odd million years and has a circumference of around 160 000 light years, it and other stars around it approach and recede from each other in their courses, and because of this the Solar System doesn’t have a fixed size, and it isn’t spherical either because stars of different masses are at different distances in different directions. I’ve chosen to define the Solar System here as the Sun plus the matter which is more influenced by the Sun’s gravity than other stars or similarly massive bodies. This is more or less how other people, including professional astronomers, define the Solar System, but it has a few anomalies. For instance, if a massive black hole entered what we think of as our Solar System, the regions where its gravity won over the Sun’s would not then technically be part of the Solar System, and when ʻOumuamua entered our Solar System recently it would have become part of our Solar System despite its origins elsewhere. There is a plasma-related “heliopause” which also constitutes a kind of barrier between us and interstellar space, constituting a fairly useful border. This is where the charged particles being shed by the Sun, also known as the “Solar Wind”, reach the point that their energy is no longer greater than that of the same kind of particles moving between the stars. The region inside this is known as the heliosphere, although it isn’t spherical because it’s like a bow wave and wake generated by a ship sailing through the sea, and there’s a long tail behind us in the opposite direction to the Sun’s movement through the Milky Way. There are currently two spacecraft outside the heliopause, the Voyager probes, but these have only managed to leave because they are moving in the same direction as the Sun and therefore have encountered the “shock” at almost its thinnest point. These will be joined at some point by Pioneers 10 and 11 and the New Horizons craft which was sent past Pluto.
This narrower part of the heliosphere is about a hundred times the distance of Earth from the Sun, or a hundred astronomical units or AU. Within it is the “termination shock” and between the two is the “heliosheath”. The reason this is seen as the border with interstellar space is that it’s where matter originating from the Sun stops moving outwards and is dominated by matter from elsewhere, i.e. interstellar space. However, there is a large cloud of objects far outside this called the Oort Cloud, which is a kind of reservoir of comets. This is vast. The planets we know of orbit within a region less than a thousandth of the size of the Oort cloud in each direction. As stars move through the neighbourhood of the Sun, their gravity slightly perturbs these objects and sometimes causes them to plummet inwards towards the planets, at which point they start to vaporise and become comets. Comets can move in three different ways. One is as usually very elongated ellipses. The closest comet of this kind has been Encke’s Comet, which took only three and a bit years to orbit the Sun and was therefore mainly inside the asteroid belt. This led to it losing most of its icy mass to space due to being constantly heated. When this happens, a comet becomes a cloud of meteoroids, and the well-known meteor showers which occasionally afflict our planet known as the whatever-ids, such as the Quadrantids or Leonids, are named after the constellation from where they appear to radiate as Earth moves through them. In the case of the Quadrantids, the constellation concerned is no longer used but the name of the shower is a monument to it. A comet can also move parabolically or hyperbolically. If it does either of these things, it will head out of the Solar System never to return, and it may in fact be from another Solar System entirely. Some comets have orbital periods so long that they haven’t been in the inner Solar System since the extinction of the non-avian dinosaurs, and in those cases it can be very difficult to determine whether they are in fact permanent residents of the system or not. Over the period of time the longest comets orbit, Earth and the Sun will have moved from the opposite side of the Galaxy, half way round their orbit.
It’s been suggested that objects in the Oort Cloud could be used to set up bases acting as stepping stones to other star systems. Although they’re thousands of millions of miles apart from each other, they form a fairly even distribution and the distances between them are minute compared to the distances to the nearest stars. Unlike the more visible parts of the system, the gravity of the Sun is not strong enough to force them to orbit in a flat arrangement like the planets do, so this could be done in any direction. This also means that comets can arrive from any direction into our part of the system. It’s possible that if we ever settled on outer Oort Cloud objects, we would technically enter another star system in a seemingly quite trivial way, from hopping between two distant members of the Sun’s and the Centauri system’s clouds, or even just by having an object move away from the Sun sufficiently to be technically more attracted by the Centauri system. The thing about the Centauri system, which is α Centauri A and B, Proxima Centauri and associated objects, is that its combined mass is more than twice that of the Sun, so it will pull on distant objects more forcefully than the Sun well before they get halfway there. In another direction is the Sirius system, which is even more massive, since one star is 2½ times the Sun’s mass and the other about equal to the Sun’s. Since it’s 8.7 light years away, this puts the limit of the Solar System in that direction at less than two light years even though Sirius is more than twice the distance of Centauri. In the recent past, i.e. the past few million years, stars have moved through the Cloud with their own clouds, causing comets to move in and sometimes hit the planets, including of course our own on numerous occasions, notably in the Gulf of Mexico 66 million years ago.
The inner Oort Cloud, alias the Hill Cloud is less perturbed by other stars and more flattened, and is the source of the comets which orbit near the plane of the planets. The reason for believing in the presence of these clouds is that comets have a limited lifetime once they enter the inner system, so there must be a reservoir providing them further out where the cold preserves them, and there are also two types of cometary orbit when considered in this way, one flattened like a planetary orbit and the other which can be at any angle to planetary orbits. The constant supply of comets has been used as an argument for a young Earth, so the alternative appears to be young Earth creationism unless some other idea can be arrived at. The objects comprising the Oort and Hill Clouds are the same as the planetesimals which originally formed the planets, and probably got thrown out of the inner system soon after their origin.
Inside the Hill Cloud is the Kuiper Belt. This is the outermost region of the system which can be directly observed. It extends from the approximate orbit of Neptune to about ten AU past Pluto’s average distance, and Pluto is part of it. It’s quite similar to the asteroid belt but much larger and contains much more mass. As soon as Pluto was discovered, its surprisingly small size and unsuitability as the planet which had disturbed the orbit of Uranus led astronomers to speculate that it was not the only world of that size and nature out there, and this was confirmed in 1992 CE with the discovery of the second “Centaur”. Centaurs, as the name suggests, are intermediate between asteroids and comets. The first, Chiron, was found in 1977 orbiting between Saturn and Uranus but at that time it couldn’t be said that it was more than just a large asteroid-like rock in an unusual place, but fifteen years later a second such planetoid was found and it quickly became clear that there was a large number of them in the outer system. This is the main reason Pluto lost its status as a planet: it isn’t that unique and if it had retained its planetary status this would’ve failed to recognise the importance of the many Kuiper Belt objects which orbit in that part of the system, often in quite eccentric orbits taking them 100 AU from the Sun.
The orbits of many of the known Kuiper belt objects beyond Pluto can be plotted to show that they are currently near their closest approach to the Sun, which suggests to me that many of them remain to be discovered because they are currently in parts of their orbits much further away. There are at least two types of Kuiper Belt object: classical and resonant. Classical objects are between 42 and 48 AU from the Sun and are able to orbit near the flat plane of the system further in. Resonant objects orbit in a certain ratio to Neptune’s year, which keeps it locked into Neptune’s orbit in a 2:3 ratio. Pluto is one of these, but all of these objects have roughly the same year length. There are also objects moving 60° ahead and behind Neptune in their orbits, and Neptune’s large moon Triton is thought to be a captured Kuiper Belt object of this kind. They also turn up elsewhere. An outer moon of Saturn, Phoebe, which orbits in the opposite direction to all the others, is thought to be such a capture too, for example.
As mentioned before, there may or may not be a large planet beyond Neptune, which would therefore be technically a Trans-Neptunian Object, and might also be orbiting outside the heliopause some of the time. Since the most common type of planet in the Galaxy, one intermediate between Earth and Neptune in size, seems to be missing from this system, it’s possible that one is around that far out which may have started further in. It was also hypothesised that there’s a much larger planet, provisionally named Tyche, is there. This has been evoked as an explanation for the asymmetry in Kuiper Belt objects, which tend to be on one side of the Sun rather than the other. Although obviously they orbit, their aphelia – the point in the orbit furthest from the Sun – are on one side. However, this has now been disproven by surveying the whole sky for such a planet, which was supposed to be four times the mass of Jupiter, out to 10 000 AU from the Sun. Another disproven theory was Nemesis, a red or brown dwarf star 1.5 light years from the Sun, blamed for mass extinctions occurring every 26 million years, which would correspond to its orbital period, but now there doesn’t appear to be such a cycle and it hasn’t been found. The surveys which eliminated the possibility of Tyche don’t refute the existence of a smaller planet up to 250 AU out, or with a highly elongated orbit bringing it between 400 and 800 AU out.
Sedna is a trans-Neptuian object around 1000 kilometres in diameter with an unusual orbit, and is incidentally the kind of object which might have been identified as a planet if the definition hadn’t been changed in 2006. It takes eleven thousand years to orbit the Sun and its distance varies between 76 and 937 AU, meaning that at its aphelion it takes sunlight more than five days to reach it. It may just be me, but this extremely elongated orbit strongly suggests to me that it’s one of many such objects which just happens to be close enough to be detected right now, but I’m not a professional astronomer, so maybe I’m wrong.
Turning to the outer planets, Jupiter and Saturn have a very large number of moons each. Some of them are minute. Leda, for example, is just eight kilometres in diameter. If their orbits were visible in the sky, both systems would look larger than the moon to us. Both of them also have three “bunches” of orbits, but of the moons known from before probes were sent Saturn’s Phoebe orbits a lot further out than the rest. Nowadays a further fifty-eight moons have been discovered orbiting Saturn beyond Phoebe, making a total of eighty-three. The much more massive Jupiter only has eighty detected moons. I don’t know why this is. Both planets have large magnetospheres with tails reaching behind them and consequently Jupiter has powerful radiation belts in which three of its four planet-sized moons, as opposed to the many more smaller ones, orbit within, making them extremely hostile. Both of these magnetic fields are generated by metallic hydrogen deep within the planets.
All the outer planets have rings. However, Saturn’s, the brightest, lightest and most prominent, are likely to be temporary. This is just me again, but I think rings are more likely to develop around larger planets because they’re larger targets for objects to be captured by and then broken up.
Inside the orbit of Jupiter is of course the asteroid belt. Although it used to be thought that it was a former planet which had broken up, adding up all the matter in the belt isn’t enough to make even the smallest known planet. The largest object within the belt is Ceres, whose diameter is around 1000 kilometres. The belt is not crowded or particularly dusty, and as I’ve already said the idea that it’s a hazardous rock-strewn region is completely inaccurate. Most asteroids are so far apart from each other as to be invisible to the naked eye from their surfaces. It’s been stated that Pluto deserves to be a planet because it has quite a few moons. The asteroid belt gives the lie to this because many of its members are piles of rubble loosely held together by their weak gravity and it isn’t unusual for them to have moons simply because the smaller lumps of rock can get dislodged and start orbiting. Asteroids are made of various substances. Some, such as Vesta, are bright and icy. Others are etremely dark and made of carbon, or they may be composed of iron-nickel alloy or stone. Their orbits tend to occur fairly close together in bands due to the action of Jupiter’s gravity, which pulls asteroids with periods in certain ratios to its own sidereal period (“year”) together. Elsewhere in the system, this may have been the main factor in causing the other planets to form. The Solar System has been described as “the Sun, Jupiter and assorted débris” because of the huge disparity between the masses of the two and everything else, even added together.
One asteroid, Hidalgo, is actually a centaur and has a very unusual orbit, more like a comet. It spends some of its time in the asteroid belt but its maximum distance from the Sun is almost as far as Saturn. Its orbit is also very tilted to the plane of the planets. As far as I know, no other object is like Hidalgo.
Within the asteroid belt are the four inner planets, five if you count Cynthia. Of these, Mars and Cynthia are only about sixty percent as dense as the others. Being close to the asteroid belt, Mars has captured two small moons from it, one of which, Deimos, is unstale and will be ripped apart by tidal forces in about 30 million years, after which it will form rings. Earth and Venus, as mentioned before, are twins, although Venus is exceedingly hostile to life and the hottest planet of all on its surface (Jupiter has the hottest interior). Mercury is the smallest planet. Neither Mercury nor Venus have moons.
Also in the inner solar system is a fairly large number of asteroids which periodically impact on the planets and other bodies within it. One of these, Icarus, has an orbit taking it out to the distance of Mars and to within 20 million kilometres of the Sun. Several asteroids have orbits locked to the planets in various ways, including Amor, Apollo and Eros, also the name of classes of asteroids with similar orbits in the case of the first two. Apollo asteroids cross Earth’s orbits, so astronomers tend to want to keep an eye on them, but due to the general disengagement people seem to feel with astronomy there is no proper monitoring program for them and no organised defence against them crashing into us and wiping us all out, and apparently that’s all absolutely fine for some reason. Amor asteroids, including Eros, a sausage-shaped object about the size of the Isle of Wight, have orbits close to that of Earth’s at perihelion and usually close to Mars at aphelion. They can also be hazardous, because the orbits of relatively small bodies tend to be less stable. Finally, Aten asteroids have average distances (semi-major axes is the official term) less than Earth’s from the Sun and an aphelion greater than Earth’s perihelion, so these too cross our orbit.
Impacts on the planets of the inner system regularly chip bits of rock off them, which may land on other planets. Consequently there are occasional meteorites on Earth from Mercury, Mars and Cynthia, and there are also many meteorites originating from the asteroids.
All of the known planets of the Solar System orbit in roughly the same plane and have almost circular orbits, the biggest exception being Mercury’s, which is roughly lemon shapes without the pointy bits. There isn’t much inside the orbit of Mercury, possibly because the sunlight is so strong there that it pushes everything away from it. Some of the larger planets have asteroids orbiting 60° behind and ahead of them in the same orbits as their own because the Sun’s and their own gravity balances at those points as well as four others. This provides a kind of transport system between the different planets, because rather than having to aim for the planets themselves, spacecraft could theoretically just aim for these “Lagrangian” points where the gravity between the various bodies balances and let themselves fall the rest of the way towards the planets. All the planets orbit in the same direction but two of them spin backwards compared to the others: Uranus and Venus. Jupiter, Venus and Mercury orbit more or less upright and Uranus is tipped over. The other planets are all somewhat tilted.
The Sun is a yellow dwarf about five æons old. Although it is called a “dwarf”, it’s actually in the top ten percent of stars by mass. By volume, it’s somewhat over a million times the size of this planet.For some unknown reason, its atmosphere is more than a hundred times hotter than its surface. It has an eleven year cycle during which its magnetic fields get wound up, shifting the number and latitude of sunspots on its surface. At the end of this cycle, it kind of goes “SPLI-DOINGGG!” and the magnetic fields straighten up again.
So that’s the Solar System, about which I will be going on and on for ages, but I will also be taking breaks and only doing it every other time. I tend to think of the bodies within the system not as asteroids, centaurs, dwarf planets and planets so much as gas giants, solid round objects and smaller irregular objects, so I’ll be dealing with them as that. There are somewhere over two hundred moons, eight known planets (nine counting Cynthia), four asteroids larger than Mimas (Mimas is an important borderline case for reasons I’ll mention eventually), eighty-four Kuiper belt objects including Pluto which are larger than Mimas, and a total of 932 centaurs, all of which are too small to be properly rounded. Some of these bodies are extremely boring or very similar to other such bodies, and there are also comets of course. Obviously I’m not going to write more than a thousand blog posts on all this, but I will probably be writing quite a few.
One thing I don’t know is whether there are more Star Trek episodes than interesting Solar System objects, so we’ll have to wait and see.
A Box Of Chocolates 