World-Building and the Real Universe

(Pardon me for the hiatus. Had to fly to Houston to do some flight testing at NASA.)

I spent a pretty good weekend doing some world-building. Since discovering the maps in the first pages of The Lord of the Rings, Redwall, and the like, I have really enjoyed sketching out maps of imaginary worlds and outlining details of the cultures and histories that play out over those maps. My maps started as knockoffs of Tolkien’s (with the bad guys sequestered in a nice, rectangular wall of mountains around some barren lands) or parallel-universe versions of the terrain around my house. Since then, though, I’ve started to inject a lot more realism into the worlds I create. Want to know where the tectonic plates and prevailing winds are on my map of Oghura? I could show you!

The Barovin Mountains are this world's ancient Himalayas. The desert is in the rain shadow of the Red Mountains - though it wasn't always, which explains some of the Oghuran-Kalatchali history!
Map of Oghura

Beyond the maps, some of my imagined cultures have fully fleshed-out languages, religions, and customs. Slowly, slowly, I’ve been compiling reference documentation on the Oghuran desert and people, the fantastical Cathedral Galaxy, and the future-universe of the Four Colonies. This weekend I was spending my time in the Cathedral Galaxy, putting together a master list of the major galactic regions and polities, along with distinguishing characteristics. Now I know a bit more about why the Imperium of the Triumvirate is split in three, how the far-from-galactic-center Traders’ Rim came to be populated by merchants and entrepreneurs, and the tumultuous history of conflict between Amseile and Shobah. I’ve also got the beginning of a couple more stories – one concerning an Imperium gladiator’s bid for freedom and another describing the Waygehn people, who evolved to sentience near the death of their star and outlived the event, leaving them homeless in the galaxy. That’s one of the most fun things about deciding to build a universe purely for short stories: I get to invent worlds, and then immediately show them off with snippets of detail!

Though the Cathedral Galaxy has some distinctly space-fantasy elements, I decided early on that it would be a universe based on hard science – though not necessarily our hard science. My short story “Conference” illustrates the point, as it shows that there are technical concepts built upon technical concepts – but at the level that Arthur C. Clarke would have described as “indistinguishable from magic.” I have no idea how the Channel Network could be set up, and building planet-size structures is clearly fantastical. (And none of you know yet what’s in The Cathedral!) But I made sure that the story was relevant to us Earthdwellers, and I lean strongly on plausible concepts to describe things like astronomical bodies or planetary orbits.

Great Galactic Map, showing major markers and the Channel Network

For example, take Heliast, the resort world on which much of “Conference” takes place. Here’s the description that conference-goers got of the world:

The tour guide explains how Heliast is an ancient world with a single moon nearly half its own size, and how that has dominated the history of the planet and made it ideal for resort paradises. A billion or so years ago, the planet spun many times under one orbit of the moon, and the energy input of ocean tides among all the planet’s archipelagoes – Heliast is over eighty percent water – gave rise to life. But nowadays, the moon orbits in tidal lockstep with one Heliast day, the prime factor contributing to the perpetual calm of its seas. The small radius of Heliast’s solar orbit leaves the planet with a reasonable day length, while the dimness of its sun places it in the liquid-water zone. Without tides, with a massive moon helping to protect the planet from asteroid impacts, and with barely any eccentricity in its orbit to create seasons, there have been few selective pressures on Heliast’s life forms. Life on the planet thus failed to diversify much, and after millions of years of evolution with few external stressors, there are now only a few ecological niches on the world. Three or four avian species, eight or ten surface-level swimmers, two or three land animals, and about six land plants are all most tourists have the chance to interact with. The rest of the planet is geological beauty for visitors to enjoy.

So, the planet’s “month” equals its “day,” but there are still many days per year and there is much liquid water on the surface. The dynamics shaped the world’s evolution. That was fun to think of! But, more and more, I am completely amazed by the strange worlds that actually exist in our own universe. Many Earth- and space-based observatories keep returning data on new exoplanet candidates, and in the last few years, the galaxy seems a lot more planet-populous than it has in the past.

This past Monday, I went to a fascinating astronomy seminar on the potential climates of Gliese 581g given by Dr. Raymond Pierrehumbert from the University of Chicago. (He’s preparing these climate models for an arXiv preprint.) Besides tying the Gleise 581 system with 55 Cancri for most number of known exoplanets around the same star (5), this planet is interesting because it falls right smack in the middle of the traditional “habitable zone,” the range of orbital radii necessary for planet surface temperatures that could support liquid surface water. Now, of course, the discovery of Gliese 581g has to be confirmed to become official – and there’s some doubt about that! – but it’s at least got scientists thinking about these dwarf-star systems in interesting ways.

Gliese 581g, which the discovering astronomer apparently would like to name “Zarmina,” is a larger-than-Earth world that is most likely tidally locked to its star. “Tidally locked” means that the planet rotates once (one day) for every orbit around the star (one year), similar to the orbital situation of the Moon around the Earth. With a little visualization, it doesn’t take long to realize that a planet with a day equal to its year would always have the same point on its surface pointing towards its sun (the “subsolar point”). So one side of the planet would be hot, and one side would be cold, and the comfortable intermediate temperatures for liquid water – and life! – would be in the narrow band of longitudes around the terminator. (Star Wars fans: this is supposedly the case with Ryloth.) Right?

Well, not really, as I found out yesterday. In turns out that global climate models of a world like Zarmina give some interesting results in terms of how water behaves on its surface.

For instance, consider a case in which the planet has water on the surface, but has no atmosphere. Water vapor is a very inefficient greenhouse gas, so the planet surface would radiate energy away into space over almost all of its surface – and any surface ocean would be frozen on top. If the ocean is global, this would be like a super-size version of Europa. However, the surface around the sub-solar point would still receive enough incident radiation that the surface temperature there might be about 270 K. So, the ice layer there might be pretty thin (meters to kilometers), and a relatively small fluctuation in the local temperature could melt the ice and expose liquid water to the surface.

So, the sub-solar point might be more slushy than icy. Now, without an atmosphere above, the exposed water would immediately boil. There might be Enceladus-style geysers blasting water up out of the slush periodically. This slushy area provides a conduit for interactions between the surface and the ocean: a way for energy from sunlight to get down into the ocean, and a way for fresh materials from the ocean to get thrown up onto the ice. Those sorts of exchanges are very important when considering habitability! And it’s pretty cool to think about anyway. What a wild world that would be!

The result is worse for habitability if Gliese 581g has an atmosphere composed mostly on non-greenhouse gases, like N2. The atmospheric dynamics from Dr. Pierrehumbert’s climate models are such that fast high-altitude winds would efficiently distribute the solar heat flux over the entire world. (Surface winds would actually be fairly slow.) But this thermal mixing would actually even out the surface temperatures, so the planet wouldn’t get a slushy sub-solar point. Any ocean would be covered with a kilometers-thick layer of solid ice.

But here’s the totally awesome hypothetical case:

If Gliese 581g has an atmosphere with about 20% greenhouse gas content, CO2 in Dr. Pierrehumbert’s model (which is apparently not unreasonable for known chemistry with silicate rocks), then there could be a circular region around the sub-solar point that supports liquid water. He showed us pictures with a global ocean over the planet, with a thick ice layer over most of the planet surface but exposed liquid water inside a circle extending to about ±45° in latitude and longitude. He called this case “Eyeball Earth.”

“Eyeball Earth:” White ice and blue water under a red sun

The liquid water ocean within the “iris” of the eye would have a surface area about equivalent to the area of Earth’s oceans, since Zarmina is larger than Earth. There could be islands or continents within the ocean, all under a red sun that never moves from its zenith.

Now I feel like my world-building capabilities have been completely put to shame by the laws of physics! Just imagine the mythologies that would arise among cultures on a planet in which the known surface world – with about the same area as our own – would actually be an almost-flat disc bordered by ice. If any adventurous Zarminan heroes pushed out into the ice, they would find themselves trekking across a barren wilderness that gets progressively colder…and darker…until they finally lose sight of their sun entirely and start to freeze. What a world!

Of course, if the surface water distribution isn’t global, then there might not be an ocean completely covering the sub-solar “iris” and there might not be an unbroken icy wall around the ocean. Nor would there be ice over the entire rest of the surface. There might be visible rock. But it would be true that any water more than ~45° away from the sub-solar point would be covered by a thick ice layer. (There’s also a complication in that a completely iced-over world is apparently also a solution to this case. The planet might alternate between an “iceball” state and an “eyeball” state.)

See? The universe is much better at building cool worlds and sci-fi settings that I am. (Makes me wish I was more like Robert Forward!) Even if the detection of Gliese 581g turns out to be spurious, that doesn’t change the fact that the physical models give these results for the same parameters. With all the stars out there, it is very plausible that many worlds like the ones I described exist!

And Zarmina isn’t the only case of the observable universe out-world-building me. Some other interesting dynamical cases arise for tidally locked planets for which the planet’s orbit is a little bit eccentric, as I found out in another astronomy talk last semester. With that slightly eccentric orbit, a person standing on the planet would see the sun rise from the horizon in the morning, reach a low-angle zenith at noon, and then retrace its steps to sink back down to a sunset in the same direction as sunrise!

Then there’s HD 209458 b – a gas planet with “superstorm” winds as fast as 2 kilometers per second rush from the 1000 C side of the planet facing its sun to the other hemisphere. Just to give you an idea how outrageously fast that is, the International Space Station orbits at a velocity of 7 km/s. Escape velocity from the surface of the Earth’s moon is 2.4 km/s. These winds are really flying, and they are driven by the simple physics of a thermal gradient.

And check out this article on Centauri Dreams about brown dwarfs and the concept of the “habitable zone,” in systems where the fading light of the star over time may have implications for evolution – and the evolution of intelligence. In short: it’s possible that, since these planets start off habitable and get progressively less comfortable as time passes, there would be a selective pressure that favors species able to mitigate their planet’s slow death – or even colonize worlds. Woah!

George Lucas couldn’t make these things up. And they can, or do, actually exist.

Edit: Check out Phil Plait’s similar comments about planets orbiting eclipsing binaries!

10 thoughts on “World-Building and the Real Universe”

  1. You are freaking amazing. I always through you had to come to writing fiction from wanting to create a theme, plot device, or character, but I see you can want to create a world. this is totally the quirky and highly informative blog of a young prof in the tradition of ol’ Prof Sanders

    Love reading you

  2. I just discovered your site from a podcast in which you talked about real spacebattletactics and over-all strategy. I read what you wrote about Heliast. I hate to point this out, but Heliast would have high biodiversity:

    It takes a while for species to evolve to fit a niche. An extremely stable environment would give life a chance to fill every possible niche. Life would be superdiverse. It seems that you might have confused diversity with complexity:

    By complexity, I do not mean the complexity of the ecosystem which would be very high on Heliast, but the complexity of the organisms:

    The occasional massextinction opens niches. The complexity of organisms is like a randomwalk, species are just as to be more simple than theirs ancestors as they are to be more complex. Cellular life started unicellular (the mean, mode, and median organisms are and always have been unicellular), so randomwalks lead to average increase in complexity. The occasional massextinction leads to an average increase of organisms in niches (some organisms in some niches might be simpler than the ones they replace).

    This is a statistical process. As an example, when the sky fell on the most avian of the nonavian dinosaurs, they were closer to our level of intelligence than the mammals. Perhaps, if the sky would not have fallen on them, spacefaring dinosaurs might have evolved tens of millions of years after the nonavian dinosaurs went extinct, but still tens of millions of years before today, spacefaring near-avian nonavian dinosaurs might have arisen. This is purely hypothetical. evolution is so stochastic that we can never know.

    How life on Heliast might be:

    I shall use like on Earth as an example. Life on Heliast surely would evolve very differently:

    Life on Heliast might be as complex as life in the Paleozoic, but much more diverse. With all possible niches filled, the ecosystem would be more complex than is or ever was on Earth. This ecosystem might have reached its current level of diversity and complexity billions of years ago with little change since then. Fossils over a billion years old would be identical to living species. I should probably email this directly to you incase you do not read this comment.

  3. Thanks for some very thought-provoking comments! I have to admit that I don’t have a background in evolutionary biology or ecology and so I’ve just been making up ideas that sound plausible to me. Perhaps I should take a second look at the ecology of Heliast if I do anything more with it!

    My rationale was that Heliast is supposed to be a world with only a small number of different settings in terms of its topography, geology, and climate; as well as few features that isolate one region from another. So, a species that evolved to fit a niche in a particular geographic area would be able to fill the same niche anywhere else on the planet. I figured that if two species with global distribution were competing for the same niche, eventually one of them would out-compete the other – so, instead of, say many different species of trees or birds of prey or crabs, Heliast would have only one each of “tree,” “bird of prey,” and “crab.”

    The other thing I reasoned was that Heliast’s environment was very stable, so there would be few selective pressures causing species to diversify further once they efficiently fit a global niche. In the absence of global volcanism, climate change, or catastrophic impacts (plausible if the orbits of other planets in the Heliast system are arranged the right way!) mass extinctions might be billions and billions of years apart. As you said, fossils from a billion years in the past on Heliast would be nearly identical with its present species. Certainly, you’re right in that random occurrences would push things out of equilibrium, but as long as that doesn’t happen very often…

    What do you think? Do those rationales sound plausible, or do the same results come from a better rationale that you can think of? Or do you think my version of Heliast really is implausible?

    The more about this stuff I learn, the more I build it into my worlds!

  4. Zerothly —— ¡0 never gets any respect! ——, you are not wrong. It is quite plausible that the biota would be the same everywherer on Heliast. The poles are not much cooler than the equator, it has a low axial tilt, and life can easily travel over the surface, so each niche would have the same organisms everywhere. The complexity of the average organism should be low because of the randomwalkprinciple:

    A descendentspecies is just as likely to be less complex than its ancestor than more complex. Cellular life starts out unicellular, so it has nowhere to go but up in complexity. Massextinctions by opening up niches lead to more randomwalking, so leads to more complex organisms on average (the new organism in a niche might very well be less than complex than the organism it replaces).

    With no massextictions to empty niches, every possible niche should be full. Each niche would be full of the same species everywhere and the species could endure for over a billion years. I shall give an example of unfilled niche:

    In Hawaii, one found no flying parasites when people landed their originally. No biting flies, mosquitoes, or anything else. Such a niche would definitely be full on the mainland of Heliast. About Hawaii, the good news is that humans introduced mosquitoes to Hawaii, so now one can enjoy mosquitoes while on vacation. It sure is nice that we improved Hawaii thus. 😉

    You are nearly right about Heliast, but someone crunching into the bush would encounter thousands of species in the first hour, but these would be the same thousands of species one would encounter in the first hour everywhere on Heliast and as fossils over a billion years ago. Without the additional rounds of random walking from the starting line of unicellularity, on average with exceptions, organisms would be simple.

  5. Ah, well then, I suppose my question becomes: What drives the creation of ecological niches? What factors determine whether there are many or few niches in a given area?

    For example, on a world with very low diversity in terms of geology and climate, I figured that the number of niches would be small, and that Earth with its widely varying locales would support many more.

  6. Earth does have more niches, but like in Hawaii with its mosquitoes, not all are full. Every niche on Heliast should be full so that one should find more species on a given square kilometer than on a given square kilometer on Earth. As for what creates niches, we must start at the basics:

    Let us suppose that the only source of energy is solar. The fastest reproducing photosynthesizer should drive all other life to extinction. We should have just 1 species of alga. ¿How do we get more species? The alga created a niche of algae-eater. An algae-eater arises. The algae-eater is so good at eating the only alga on the planet, that it opens a niche for algae it can not eat. Ther kinds of algae arise for fitting these niches and new herbivores arise for eating these algae. The algae and the herbivores support parasites and diseases, thus creating these niches.

    Predators for the primary herbivore arise, thus suppressing its numbers, making room for new herbivores in the niche, thus dividing the niche into subniches. New niches are created thus in each environment on Heliast, Earth or anywhere else until, the new niche of parasite of a parasite on a scavenger has such a small population size that it must go extinct.

    Looking at the Ediacaran through the CambrianExplosion (which despite what creationists claim, took tens of millions of years), and the OrdovicianRadiation, this is exactly what we find happened on Earth.

    Let us look at the iPod:

    People want portable music. The iPod fills a niche firstly populated by the SonyWalkMan. MP3-playesdisplaced the WalkMan-like and DiskMan-like players in the late 1990s because they hold more music. In the early 2000s, the iPod came to dominate this market because it is easier to use than most of the competition and has an higher capacity than most of the competition. This opened niches for various parasite of the iPod called third-party accessories. Each parasite took a slightly different niche on its host and they proliferated until any remaining niches would have a population-size too small to support them.

    Stability should lead to many species per square kilometer. This should start off as a single species of alga forming a monoculture and then niche-creation should lead to a sort of Ediacaran/CambrianExplosion/OrdicianRadiation-like process.

    It is too bad that Heliast does not have too many environments. Imaging a world without any massexinctions in billions of years with an axial tilt of 45 degrees, constant tropical temperatures, but with polar temperatures varying from negative -40C in the winter to positive +40C in the summer. With Huge mountains reaching into the stratosphere, plains, deserts, jungles grasslands shallow oceans, deep oceans, isolated continents, et cetera. With stability leading to a large number of species per square kilometer and so many different environments, it could have nearly a billion species instead of just the 50 million species Earth has.

  7. Well, perhaps I can chalk Heliast up to a weird fluke that has gotten itself into some kind of equilibrium, and the next world I build can be different!

  8. As I wrote, you are mostly right:

    with all of the continents connected as well as the oceans, almost no axial tilt, few environments and the poles being not much colder than the equator, life on any point on land would be much like life on land everywhere else. Life anywhere in the oceans would be like life elsewhere in the ocean.

    I just finished reading your short stories. I cannot wait for you to finish them. ¡They are great!

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