I’m running a new campaign. I ended up as DM because I ended up having the most experience with D&D, despite that being almost none at all. My world takes place on a massive bishop ring. This post will talk about some of the implications of running a campaign in such a world. For the uninitiated: Bishop Rings

First, some base assumptions about what sort of campaign I want to run.

1. This is fantasy, not Sci-Fi. Despite the setting taking place on a structure traditionally seen in Sci-Fi, the people living on it will your typical agricultural society. The people who built the ring will have, even in their prime, built temples out of stone. Swords and spears. No rayguns.
2. The ring has natural terrain, or appears too. Even though it was obviously (to us) artificially constructed, for some reason it still has mountains and deserts and bogs.
3. Low-magic. Wizards, Sorcerers, and Adepts all exist but are relatively rare. Magic doesn’t replace technology, but did compliment it in the case of the Ring-Builders.
4. Fallen World. The ring has seen better days.  Large swathes of wilderness. Their might’ve been an apocalypse, but if there was it was a long time ago. People are more concerned with the breakdown of what centralized authority there once was. You know the deal.

Size and the Lie of Gravity

So, the ring. Gravity normally wouldn’t affect those on the interior of the ring, but the rings rotation can provide a facsimile of gravity, which it does. It completes a rotation every day, for reasons that will become obvious shortly. The exact size and radius of the ring can be determined later. The edges are massive mountains, miles high, designed to keep the air in.

To provide Earth-like gravity while having an orbital period of 24 hours, we need the equation

a ~ 10 m/s = r(2pi/T)^2

Where a is the centripetal acceleration (the “gravity of this planet”), T is the period of rotation (24 hours) and r is the radius of the ring. Solving for r, I get 1.9 million kilometers. This is very large, which isn’t necessarily ridiculous. Okay, building such a structure is, but they had magic. No, in the grand scheme of inter system scales, a million kilometers is almost nothing. The distance difference between Venus and Earth from the sun is 40 million kilometers, and 70 million in the case of Mars and Earth. Fuck it, we’ll go with it.

The land area of the ring is simply the circumference of the ring times the thickness. For thickness we’ll say 3000km, so we get an inner surface area of 36 billion square kilometers. A lot of this will probably be taken over by radioactive blasted hellscape deserts and oceans.

Tides are going to be ridiculous due to the massive radius of the ring, but I have an idea for that later on.

Sky, Night and Day

For the day and night cycle, I originally had a convoluted idea involving solar shades that were destroyed, cobbled together and suspended from a giant tower that extended to the center of the ring, but discarded it because it was too complex and probably wouldn’t work the way I wanted. Instead I’m going with an axial tilt that casts half the ring in light and the other half in its own shadow. The solar shades still existed at one point and were wrecked, and I love the central tower so much that I’m keeping it, but this just makes thing simpler. In reality, their may not be an axial tilt that exactly accomplishes this due to the geometry of the ring, as it may not be wide enough to occlude the sun. Technically I have enough physics/astronomy background to figure out if this is true… but for now we’ll say there are long sunsets and sunrises. At the outer edge of the border mountains, 200km up, day is probably constant.

This has the added effect of making the equinoxes periods of darkness, as one half of the ring is in the shadow of the other half, a process which probably lasts a few days. I could use the apparent size of the other half of the ring to actually calculate the duration of equinox eclipse, but I feel that probably isn’t needed at this point. The other half of the ring is nearly always visible, and is the brightest object in the night sky, by far.

Seasons are trickier. I could do away with them entirely and make book keeping a lot easier, but I feel most agricultural societies almost need some kind of consistent season cycle to function. The way seasons work on Earth isn’t going to work here; every part of the ring passes under the area of direct sunlight because of geometry. Right now I’m playing with a highly elliptical orbit, but that locks me into loooooooooong winters. I’m also considering making the star the ring orbits a binary, with a resonance between the dimmer companion’s orbit around the barycenter and the rings orbit, but I’m not sure if occlusion by the dimmer companion would actually lower the energy received by the ring enough to cause a seasonal change. I’m still looking into it, but now that I think about it, that could be really cool. It doesn’t even have to be a companion per se, maybe just a large planet or brown dwarf closer in. What the hell, its in. If we can use occlusion methods to detect binaries, then they can probably cause seasons. A solar eclipse can cause the temperature to drop by several degrees, so I feel this is a reasonable enough approximation.

The seasons are provided by a brown giant (really, they ought to be called purple giants, as they are hypothesized to be magenta in color) with a 2:1 orbital resonance with the ring. For part of the year, every year, the brown giant is between the ring and its bright F-type star. The brown giant is so large that it take a few months to move out of the way entirely. The solstices are when the dwarf is in inferior conjunction (directly between the sun and ring) or at superior conjunction, where it is directly on the opposite side of the sun. I could do some calculations with apparent size and flux, but that shouldn’t be strictly necessary for now.

Climate

Other considerations include wind patterns, terrain, and the underground. My knowledge of atmospheric science is limited, but I understand that most of the prevailing wind directions speeds are determined by temperature differences at the poles and equator, neither of which exist on a ring world (well, not in the same way anyway). So I can’t help but feel the wind will, because of inertia and relative motion, appear to be blowing in the direction opposite the rings rotation, as a general rule. In fact, I’ll go ahead and say that breezes in this direction are near constant, and are often used as a navigational tool by the inhabitants. Directions aren’t called East and West, they’re called Zephyr and Anti-Zephyr, with or against the wind. How seasons affect this is yet to be determined but I imagine summer will be stormy times for coasts facing Anti-Zephyr. The Northern and Southern directions are not nearly so universal.

I imagine due to the cooling effects of the border mountain, the “northern” and “southern” regions will actually be cooler than central regions, sort of like what we see on Earth because of insolation differences at different latitudes. Coastal regions bordering the mountains will especially be affected, since the cold water flowing down from the mountains will cool the nearby oceans.

The Deep

The underground can be whatever we want to be. I like how the Classical Mayan’s imagined the underworld as watery place, in addition to a dark and dangerous one. The creators used their underground areas to store dangerous things, in addition to water, both fresh and salt. Remember the tides I mentioned earlier? Well, conventional knowledge and long derivations say that the tides will want to bulge out towards the sun on the close side of the ring and away from it on the far side, but all the water is stored on the inner surface of the ring. What if the underground areas of the ring were designed to store some of this water, and give it a place to go, to prevent them from being too extreme? That could work.

Cenotes will be common on the ring, and were once access ports to these repositories that have long since eroded to more natural shapes, and covered with lakes and rivers in wetter areas. Like many cenotes, the underground as a whole will be split into two layers: freshwater and saltwater below, because its heavier. The layers aren’t at discrete depths, or necessarily even continuous with themselves throughout the entire circumference. Naturally, the underworld dotted with submerged caves  filled with the accumulated and dangerous castoffs of the previous civilizations that inhabited the ring. Below the reservoirs/caves are the control structures of the ring, not made of stone but of wondrous materials capable of holding this mess together.

I’ve also decided that the progenitors of the ring will take some Mayan flavor. Arcane script, the language of magic and wizards will be visually similar to Mayan glyphs, for example

NEXT TIME: The setting details that people are likely to actually care about. History and geography.

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