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Month: August 2018

Human Destiny Reference Map Complete!

Human Destiny Reference Map Complete!

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Okay, after several weeks of effort, I’ve finished my project to use the Architect of Worlds design sequence and place habitable worlds throughout the “solar neighborhood.” I’ve also finished producing a map of the region, based on those data.

The Human Destiny setting ended up with 28 more-or-less habitable worlds, and two colonized star systems without habitable worlds, in that ten-parsec radius from Sol. That’s out of roughly 328 stars that make up 265 star systems, indicating an average of one habitable planet for every nine or ten star systems. A bit more than I expected when I got started, but it’s a figure I can work with.

Here’s a thumbnail for the final draft map:

It’s a pretty huge file, so you might do better to download it and view it locally. Alternatively, here’s a link to the map’s page in my DeviantArt gallery.

At this point, I have a couple of things to publish here over the next few days. One is a review of the large-scale galactic situation in the Human Destiny setting (how common interstellar civilizations are, how they are likely to be structured and so on). Now that I have a plausible count of Earth-like worlds, I can finish those notes.

It also occurs to me that I now have a list of interesting worlds from the new map – I should draw up some capsule descriptions for those. I seem to be converging toward being able to publish a mini-worldbook in GURPS terms for this setting.

More long-term projects: now that I’ve given the Architect of Worlds system a thorough test drive, I need to go ahead and polish up and upload the working draft of the planetary-system design chapter. I also have a whole sheaf of case studies with which to develop and test a new section, on the design of individual worlds. I think I’m also prepared to produce a new draft of the next Aminata Ndoye story, a novella titled In the House of War, which will be the next item to get published. Busy, busy – but at least I’m continuing to work through my Gantt chart.

Status Report (21 August 2018)

Status Report (21 August 2018)

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Still slogging along through the HIPPARCOS catalog – every day, I work through a dozen or so stars (and find myself wishing I had just written a C program for this already). At the moment I seem to have gotten through 276 entries in the database, out of a total of 327 reaching to the ten-parsec radius. Out of those stars, 23 have at least one planet with a complex biosphere, and at least a few systems have two each. It’s looking like a trend of about one in ten to twelve stars will have a more-or-less-Earthlike. I’m not bothering to count the “pre-garden” worlds, with liquid-water oceans but too young to have developed a post-Cambrian biosphere. There are quite a few of those.

Today I sat down for a few hours and started drawing a map of nearby space, including all stars of K class and above, and those few M-class stars that have Earthlike worlds. I’m using the same techniques that I once applied to this map of the solar neighborhood, and I imagine the end result will look similar.

I’m using a galactic coordinate system this time, rather than the usual equatorial coordinates, so a lot of stars will look like they’re in the wrong place if you’re accustomed to the maps from (e.g.) the 2300 AD or Universe tabletop games. I’m planning to include the appropriate coordinate transform in the Architect of Worlds draft, when I get around to writing the “using real astronomical data” section.

I’m also marking down tentative names for Earthlike worlds, instead of an abstract “resource value.” My vision for the Human Destiny setting has evolved quite a bit over the past few years. Today I’m assuming that the dominant interstellar civilizations won’t spend all that much time or effort exploiting star systems that don’t host complex biospheres. So the systems of greatest interest are going to be the ones that humans (eventually) settle.

If anyone’s interested in glancing at the work in progress, here’s a link to the appropriate entry in my Scraps folder. Only about twenty or so stars placed so far, or a little under one-third of the way through my data set. This is slow work, but it’s starting to come together.

Meanwhile, I’ve been working on a revision to my old notes about the density and structure of interstellar civilizations. Here’s a link to an article I wrote a few years ago, which lays out an argument about the limits to an interstellar civilization’s growth. (That article is also one of my few contributions to Winchell Chung’s Atomic Rockets website, in fact.) The Human Destiny setting incorporates that notion into its basic assumptions. I’ll probably publish those notes here within a few days.

Status Report (11 August 2018)

Status Report (11 August 2018)

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Still working through my data pull from the HIPPARCOS data set. I haven’t found any more planetary systems that the draft Architect of Worlds model simply won’t fit, although the famous Gliese 667 C system came close.

One thing I have discovered is that my assumption about red dwarf stars seems to have been premature. A little further research tells me that the photosynthesis problem isn’t an absolute deal-breaker. The problem isn’t that photosynthesis is impossible under red-dwarf starlight, it’s that an early photosynthetic organism would have to adapt to long periods of visible-light scarcity, punctuated by the nasty stellar flares young red dwarfs tend to generate. One might imagine mats or colonies of photosynthetic microbes that drift to the surface of a planet’s ocean to take in the sunlight, then submerge to ride it out when flare weather sets in. Eventually, most red dwarf stars seem to settle in and stop producing major flares, so if their planets can give rise to life at all, evolution to complex biospheres seems at least possible.

So, rather than forbid red dwarfs from having garden worlds at all, I’ve decided to impose a penalty, requiring them to take a lot longer to develop complex biospheres. Even so, since red dwarfs burn so steadily over many billions of years, an ocean planet has plenty of time to work on the problem. Red dwarfs that are at least as old as Sol, certainly the ones that are a few billion years older, are possible candidates.

I worked out a set of criteria to determine whether I should work out a red dwarf star’s planetary system at all: at least as old as Sol, bright enough that the habitable zone falls out where the inner planets are likely to orbit, and with metallicity high enough to permit terrestrial planets at least one-quarter as massive as Earth. I’d say maybe one out of three red dwarfs in the solar neighborhood have fit the criteria well enough for me to break out the calculator, spreadsheet, and dice.

Now another facet of the new model comes into play. The draft model often generates systems of planets whose orbits are more tightly packed than one would expect, just looking at our own system. Which in turn significantly increases the probability that at least one planet will sit in the liquid-water habitable zone. In fact, sometimes I’m getting two planets in the zone in the same system. That’s not a result that the GURPS Space 4/e model would have produced very often, if ever.

The upshot is that although any given red dwarf is unlikely to host a garden world, there are so many red dwarfs that I’m getting a significant number of them. Lots of “eyeball planets” out there, it seems; possibly as many as the more Earth-like worlds with reasonable day-night cycles.

So far, I’ve worked out planetary systems to about 25 light-years from Sol, including all the K-class and hotter stars, now also including all the red dwarfs that seem to be plausible hosts for garden worlds. 168 lines in the HIPPARCOS database, although a handful of those aren’t actual stars, and 16 stars that have complex biospheres present. Looks like roughly one out of ten stars is giving me at least one garden world. More than I expected, actually, but it’s a result I can live with.

Status Report (5 August 2018)

Status Report (5 August 2018)

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Most of my effort over the last few days has been directed toward two tasks. First, continuing to test the Architect of Worlds model for planetary systems by generating collections of worlds for stars close to Sol. Second, using those results to motivate the first definitions for the next stage of the design sequence: determining the physical properties of an individual world.

The first is going as well as can be expected. So far, I’ve only found one star system that I flatly can’t model properly (the HR 8832 system, about 21 light-years from here, which is believed to have an even stranger collection of super-Earths and close-in gas giants than usual). Otherwise, I’m getting a very plausible set of planetary systems, a significant improvement over the results I would have gotten from the old GURPS Space 4/e design sequence.

As far as the second task goes, I’ve had something of a breakthrough: I’ve found a model I can live with to help the user decide whether a given planet is tide-locked to its primary star or not. It’s a horrible kludge – but the question of how long it takes a planet to tide-lock is very complex, and there’s no consensus in the literature about it. If a planet could be modeled as a uniform and perfectly elastic body, the math simplifies pretty well, but planets just aren’t like that. The equation I’ve come up with seems at least plausible, in the forty or so star systems for which I’ve generated data so far.

Right now, I’m wrestling with how to decide whether a given planet (or moon) has a substantial atmosphere or not, and whether it has oceans or not.

In GURPS Space 4/e, I kind of took a backwards approach – I had the user decide which of several categories a world fell into, and then he generated the world’s mass, density, and so on to fit. I think that was slightly more useful for the gaming context, but the math was kind of annoying (not least because SJG editorial policy forbade me from using SI units, so I tried scaling everything to Earth and the Sun, with weird outcomes). The math is a bit more straightforward doing it the other way – define a planet’s mass and density, then figure out what its surface environment will be like.

Of course, now I have to wrestle with questions like why Mars has almost no atmosphere despite being massive enough to retain molecular nitrogen and carbon dioxide (and it can’t just be because Mars has no magnetic field to speak of, because Venus doesn’t either, and it has a very thick atmosphere). Or, say, why Titan has a substantial atmosphere when the almost identical Ganymede has none.

Slowly, a classification scheme is emerging, but it will probably be a few more days before I’m happy with it.

Meanwhile, the upcoming week is going to be unusually busy at the office. I’m teaching one course, taking a second course, and facing impending deadlines on writing two more courses after that. Generally, my life is not quite that full! I may or may not have a lot of time to play with my worldbuilding over the next few days. We’ll see how things go.