Planetary Classification

Tony Harris asks:

It sounds as though you have some kind of planetary classification scheme set up. Care to share how it works? :please:

Well, yes, yes I do.

(Let me start out by saying that it does not, however, define what a planet is, except inasmuch as the classification scheme’s largest category stops at 2.5e28 (i.e. 2.5 x 1028) kg, which is about 13.2 Jupiter masses, at which point it gets kicked over to the stellar classification scheme at the bottom end of dwarves, brown.

Insofar as there is a definition of a planet used there, it’s dreadfully informal and would run along the lines of:

  • Orbits a star (other than a brown dwarf that is itself part of another star system);
  • Masses less than 2.5e28 kg;
  • Masses enough to be approximately spheroidal;
  • Is cared enough about by travelers to be listed in Leyness’s Worlds, or some other casual reference that isn’t an astronomer’s catalog or a space pilot’s ephemeris.

So, Pluto, despite being a gelidian-class planetesimal by the scheme, is a planet because it has enough historical significance and popular interest that it’s undoubtedly mentioned in the hypothetical Leyness’s Worlds: A Guide To Places No-One’s Discovered Yet, Except The Natives Who Obviously Don’t Count, while the other plutoids or whatever we’re calling them these days aren’t, because they don’t.)

As for the scheme itself: well, it’s kind of long and complicated and unfinished, especially since the universe keeps surprising us with New Facts About Planets that need to be fitted into it as if they’d been there all along, so I hope you’ll forgive me for not sharing the whole thing. But I don’t mind talking a bit about it, so I’ll do that.

The primary distinction it uses when classifying – and it classifies everything from small rocks through moons and on up, not just “planets” – is mass, which has the advantage of encompassing a fair bit of other useful information. Using mass, it defines five basic categories: small bodies (< 6e20 kg; too small to maintain hydrostatic equilibrium); planetesimals (6e20 kg to 9e23 kg; can maintain hydrostatic equilibrium); lithics (9e23 kg to 3e25 kg; tend to clear out their orbits and self-sustain geology); helians (1.8e25 kg to 1e26 kg; big enough to retain helium, but not yet gas giants, and yes, this overlaps with the one before it); and gas giants (5e25 kg to 2.5e28 kg, and so does that). There’s also a sixth class, wanderers, which defines those odd planetary-massed objects that aren’t gravitationally bound to any star and just drift about in the deep.

The overlaps, incidentally, are because none of these top-level categories are intended to be particularly strict. The Imperial Grand Survey learned long ago that the universe is a very complicated place that doesn’t fit itself into neat boxes for their convenience – so the boxes are a mite fuzzy, and worlds are assigned to the class that bests fits them even if technically they’re a little too massive for the top-level category that world sits within.

So, the categories: small bodies are asteroids, comets, and similarly-sized moons, for the most part, subcategorized primarily by composition and solidity (aggregate-class rubble piles vs. silicaceous-class stony asteroids, for example). The comets are also divided based on whether they’re icy bodies orbiting peacefully in the outer system, or which are actively plunging through the inner system.

Planetesimals are mostly large asteroids and moons, divided up by age (are they just forming?), composition (rocky or tarry or icy), level of geological activity and its source (mostly passive, due to eccentric orbits and epistellar heating, due to tidal flexing, due to internal heating, etc.

Vesta, Ceres, Luna (selénian-class), Europa, Titan (galínilacustric-class), even Mars (eutalentic-class), they all fall somewhere into this classification.

Lithics are the big rocky ones with substantial atmosphere. Their subclassifications are much the same as the planetesimals, plus additional ones: age (forming or dying), water content (xeric through thalassic to pelagic – a global ocean, in these terms) and their methane and ammonia equivalents, presence of a biosphere, presence of halogens, and so forth. There are more lithic subclasses than there are subclasses of anything else, just about, partly because they’re more varied, and partly because they also attract a great deal of interest.

Earth (sylithotectonic-class) fits in here.

Helians get the aborted gas giants, plus a variety of superterrestrial rocky worlds with thick, helium-rich atmospheres. Its number of subclassifications is relatively limited, simply because there’s a very fine line between retaining helium at all and ending up among the…

Gas giants, divided principally by mass (subgiants, dwarf giants, mesogiants, supergiants), and then principally by their orbital positioning (epistellar, within the snowline, beyond the snowline) which defines most of their composition and behavior.

Around here, they would include, for example, Jupiter (melíeréan-class) and Neptune (déiran-class).

So, I hope that was an interesting peek into how the IGS planetary classification system works. I’m happy to answer a bit more, if anyone’s interested, but as I said, I don’t really want to put the whole thing out there until it’s suitably finished and polished.

Trope-a-Day: Numbered Homeworld

Numbered Homeworld: Averted.  As we mentioned way back in Naming Your Colony World, inhabited systems generally do get named objects, if only because they’re easier to remember.  Even uncontacted alien homeworlds get names, often a pronounceable transliteration of whatever the local name is, out of some respect for local sensibilities… and ease of memory/reference.

(Yes, this implies that Vonis Prime isn’t really called Vonis Prime…)

Trope-a-Day: Naming Your Colony World

Naming Your Colony World: Examples of most of them exist in various places, although the Imperial Grand Survey works really hard to discourage people from naming anything New Anything, to the point of refusing to register the names, on the grounds that in deep time, eventually naming things New New New New New Whatever is too damn silly for words.

Beyond that, most of them are literary or mythological references, with a smattering of egopoli and symbolic names.  Numbered names are generally reserved for unexplored systems (most of them beyond the periphery of the Associated Worlds), and star names are generally not found per se, although generally, settled systems tend to be referred to, even on star charts, by the name of the primary settled world/main habitat in the system, rather than that of the star; which is not to say that the star doesn’t retain its own name separate from that of the world in formal usage, of course.

Questions: Economy and Habitats

Got some more questions! Jamie asks:

It strikes me as odd that at the technological level the Eldrae work at that they appear to be working under an ideal capitalist system in an era of post scarcity technology. How is wealth determined? What is the currency based on? What kinda of inequality is there if any?

Well, the thing to bear in mind about “post-scarcity” societies is that virtually all of them are actually only “post-material-scarcity” (or “nearly-post-material scarcity”, which is how I’d describe the Core Economic Zone polities and regions in the Eldraeverse.) Some things tend to remain scarce – ideas (especially if we assume that inventors, designers, authors, and so forth like to be paid for their work for reasons over and above what the money can buy them, which as an author, I’m pretty sure of), personal services, availability (only so many people can attend X event), etc., etc.

This is true even if we step out of my universe and examine the ur-post-scarcity example, Iain Banks’s Culture, in which a plot driver running through many of the books is the competition to get into Contact, or Special Circumstances, which by no means takes even all the qualified people who want to get in. In Look to Windward, we also see the case of a live concert timed to match the light from a particular supernova – and thus obviously limited to only that one particular place and time and audience – cause such perceived scarcity that even the people who are very smug about “money is a symptom of poverty” immediately reinvent scarcity economics and trading favors in the quest for tickets.

So that’s why they still need an economic system. (Well, that, and nearly-post-material-scarcity only means that mining, generating, and manufacturing is super-cheap, not free, because it still takes energy and thought to do – thermodynamics, it is a bugger. People may only be paying the equivalent of $20/month, easily covered by the Citizen’s Dividend, for the right to manufacture a giant pile of consumer goods every day, but that trivial cost is still there on the back-end.)

As for capitalism – well, now, I find that something of an unfortunately loaded term in *here*’s politics, so I try not to use it to describe things *there*. Their system is both propertarian – inasmuch as it esteems private property, and makes great use of property rights in various areas – and agorist – making use of free markets (which, given their views on the essential nature of consent, is close to the only ethically permitted option).

When I say “loaded”, of course, one of the things I mean is that people assume that capitalism includes only for-profit corporations (which the Empire’s system doesn’t – as the link above says, CEZ economies have an extensive agalmic component, and usually support healthy gift economies, open source communities, alternative internal economic arrangements (co-operatives, ecodemocracies, etc., etc.), the bounty economy, the street performer protocol (like Kickstarter), etc., with wage-based employment (which is almost nonexistent outside indenture – see here, here, and here). It is, if you will, also a free market in free market types.

…and it stays that way, essentially, ethical issues aside for the moment, because the Empire got to become a wealthy nearly-post-material-scarcity civilization by being organized that way, and the wise man does not kick away the ladder that got him where he is today. Especially if he’s still standing on it.

As for how the currency’s based, there’s a good explanation of that here (look down in the article; the first part covers why it’s Very Much Not Gold). It’s essentially fiat, but a peculiar kind of independent fiat designed to match the currency base accurately to the production capacity of the economy (because inflation is a form of robbing creditors to pay debtors, and deflation is a form of robbing debtors to pay creditors, and that is just not on, no sir).

As far as inequality is concerned, I can do no better than point you at the explanation here: Trope-a-Day: No Poverty.

The other thing that seems odd is that they are very planet focused and mentions of space habitats of all shapes and sizes seems rare. How common are Eldrae habitable worlds? What makes planets more useful than more energy and resource efficient habitats? How have they varied the basic habitat designs?

Um, not sure where you’re getting that from. I seem to recall more than a few mentions of one habitat or another, and canonically about three-fifths of the Imperial population are spacers, only two-fifths living on planets. (By no means all of which are habitable, if by that you mean “shirt-sleeve habitable”; most of the populated planets in the Worlds are partially-terraformed Mars-type worlds, which are actually much easier to deal with than existing garden worlds, habitability-wise.) There’s a certain bias towards garden worlds in the Thirteen Colonies, back in the Imperial Core, because of the preferences of the old subluminal colonization days, but in general, it’s not so; and the list of “habitables” tends to include worlds like Sialhain (Venus-like, colonized in aerostats), and Galine (Titan-like), and so forth.

As for why planets – why not planets? People started out being used to them. Sometimes people like seeing landscapes that someone doesn’t have the architectural plans for, or smelling a few trillion tonnes of aeon-old biomass on the wind. (Or maybe they just like wind, who knows?) Or, y’know, because planets have oceans, and while there are aquatic habitats,  you’re not getting the cetacean uplifts out of the Big Puddles any time soon. It’s not a decision anyone’s making out of questions of efficiency, being nearly-post-material-scarcity, and all; it’s a decision people make because they feel like it, and why not?

As a side note: garden worlds are also extremely useful and valuable because they have ecologies, which are very information-dense. And even in the most crassly commercial sense, an ecology is a giant library-cum-research-program of new biotechnological and nanotechnological tricks to draw from. It’s just good business.

(Outside the Empire and other transsophont cultures, of course, many people live primarily on planets because they’re too Luddite or biochauvinist to modify themselves to live comfortably long-term in microgravity. But, hey, someone’s got to be the meek who inherit the Earth, right?)

Habitat-wise: well, I’m going to keep the details under my hat a bit until we see them in fic, but teaser-wise, what I will say is that while there are some O’Neill cylinders and the like, the majority of them could be classified as modular structures or asteroid beehives, operating in microgravity – and even the cylinders tend to operate under low spin gravity. After all, why live on a faux planet when there are plenty of real planets around? Spacers prefer to live spacer-style among spacer-style architecture, by and large.

P is for Planets

(It’s been a while since I’ve worked on this project, for one reason or another, starting with being somewhat blocked on Q. If you’re a relatively new reader who’s never seen the previous entries, therefore, I suggest clicking on the “picture dictionary” tag, at the bottom of the post, to see them all.)

P is for Planets,
Life’s havens in space.
They once were our cradle,
The home of each race.

Q is for Quanta,
The tiniest things!
Quarks and neutrinos,
Photons and strings!

R is for Robots
Which work all the day.
To keep our worlds running,
And failure at bay.

(Yes, I know the physics limps a bit in the middle one. You try making rhyming couplets for posthuman three-year-olds…)