Sharrukin's Palace

Since Architect of Worlds was published in 2024, the book has held up pretty well. We’ve gone through seven minor-version releases, each of which has corrected minor errors or made patches to the design sequence. “Minor” as measured by the fact that we haven’t had to repaginate anything – I think the biggest tranche of new text so far was four short sentences long. Here’s a link to the current errata list.

Science marches on, of course, and in any case many of the models described in Architect of Worlds are deliberately simplified to some degree for ease of use. While interacting with readers, and especially while working with Ad Astra Games on other projects, I’ve found myself making notes about ways to improve and add to those models.

For example, I’m currently supporting a long-term world-building project for Ad Astra Games – updates to their Ten Worlds science-fiction setting – that is already motivating new research. The “Ten Worlds” of that setting are often only Earthlike by courtesy; they tend to have odd features that make them poor copies of long-lost Earth. Which, of course, means they often manifest special cases that fall outside the usual design parameters of the Architect of Worlds sequence. I’m currently doing research to help put solid scientific justification behind the Ten Worlds planetary designs, where possible, and that’s providing fertile ground for possible improvements to the Architect models.

Eventually (and by that I would estimate 2-3 years from now) I’m going to have enough new, refined, improved models that a significantly new design sequence is likely to be called for. That will lead to a Second Edition of the book. I’ll likely make note of some of those potential changes in this space, just to keep readers up to date on what they might expect in that Second Edition.

So far, I’ve identified three good candidates for new modeling:

Tweaks to the design of planetary systems (Steps Nine through Twelve): The Architect design sequence as written doesn’t quite cover all the exoplanetary systems we know about today, not in fine-grained detail.

For example, the putative exoplanets for Tau Ceti (assuming those actually exist) are remarkably massive and the current design sequence has a hard time matching them.

Meanwhile, the well-understood TRAPPIST-1 planetary system doesn’t quite fit – given the masses of the known terrestrial planets in that system, Architect implies there should be at least a few gas giants as well, and we haven’t detected those. Further research seems to be indicated, to find ways to modify the existing sequence to better accommodate the special cases we’ve seen.

New features for the atmospheric-retention model, to better handle hydrodynamic escape due to extreme ultraviolet (EUV) radiation (Steps Twenty-Two and Twenty-Six): There’s a provision in the current edition (added very late in the design process) that attempts to model the way EUV radiation drives off portions of a terrestrial world’s primordial atmosphere. It’s not a terribly elegant provision, and it’s probably too harsh on some of the special cases.

Meanwhile, it occurs to me that modeling hydrodynamic atmospheric depletion could also be extended to the case of ongoing atmosphere loss for worlds circling flare stars, which can continue to generate EUV bursts for billions of years. So this is a good candidate for a more fleshed-out model. Probably involving a more nuanced approach to computing a world’s M-number.

For example, we might compute a “young primary star” M-number that measures its early EUV output and mostly just affects whether the world retains primordial hydrogen and helium. Then a “sustained M-number” that mostly models simple thermal escape, but which also takes into account the continued EUV output of a flare-star primary.

More sophisticated modeling of atmospheric greenhouse effect (Step Thirty): The existing model for final atmospheric composition and greenhouse effect is actually fairly sophisticated as-is, but even so it does simplify a few factors away.

For example, we normally don’t think of the diatomic molecular gases in Earth’s atmosphere (the nitrogen and oxygen) as being significant for the greenhouse effect, and the current edition of Architect ignores them entirely. However, for worlds with denser atmospheres (such as “super-Earths”), collisions between air molecules become significant in causing greater absorption of far-infrared radiation and therefore promoting greenhouse effect. This makes another good candidate for improvements to the existing model – probably the biggest challenge I’ve come across so far, because real-world mathematical modeling of atmospheric greenhouse effect tends to be very complex.

There – that should give you some idea as to the kind of subjects I’m working on for that eventual new edition of the book. Watch this space for more updates, which I suspect will be very occasional at first, but will become more frequent as the new edition comes closer to being a reality.