Aetrimonde

Today, I’m going to talk about the actual world of Aetrimonde, by which I mean the planet and the solar system that it exists in, and some of the everyday consequences of things like lunar cycles. Notes in italics are out-of-universe references using Earth as a point of comparison.

I have just enough knowledge of physics that I think I was able to work out the math behind the lunar orbits correctly, but if you’re better at astrophysics than I am and you think I’ve gotten something wrong, let me know!

Before I get into that, though, I’ve got a poll for you: I’ll be continuing this Gazetteer series by covering the Great Polities of Aetrimonde, which I’ve discussed briefly in a previous post. So, which one would you like to see more about first?

The Planetary System

The world of Aetrimonde occupies a planetary system orbiting a yellow sun. Astronomy is an important field of study on Aetrimonde, for reasons discussed below, and local astronomers are aware of six planets in the system, including Aetrimonde itself. However, the more distant of these planets were only discovered recently, and given that there is still plenty of room for telescope makers to improve their craft, the astronomy community suspects that there are still more planets that are still beyond the reach of their vision.

• Caldimonde, the Forge, closest to the sun, is a scorching hot world. Observations through Aetrimonde’s telescopes are indistinct, but suggest that the planet rotates slowly (just once every three Aetrimondean years), with the side facing the sun growing hot enough to melt stone and metal before cooling as it rotates away.
  • The parts of Caldimonde that are not currently molten are a rust-red, and even before its forge-like environment was discovered, it was associated with Deum Making, god of the forge and of craftsmanship in general. Various legends hold that finishing a work of craftsmanship when Caldimonde is at its zenith will make the result blessed, lucky, or just less likely to break.
• Nubrimonde, the Jewel, is visibly covered in clouds through telescopes, and is believed to be hot and humid. Even before the invention of the telescope, it was observed to cycle through shades from yellow to violet. More detailed recent observations suggest that the planet has an atmosphere containing several different gases, with some atmospheric process that churns up the gases and periodically brings different ones to the top.
  • Nubrimonde is associated with Deum Reveling, god of, among other concepts, aesthetics. As one of Deum Reveling’s other domains is joy and celebration, there are numerous festivals held at various points of significance during Nubrimonde’s transits. Most of them have no deeper meaning, and are simply excuses to hold large parties.
• Merimonde, orbiting slightly inside Aetrimonde’s own orbit, is a slightly wetter and warmer planet. Because it is the planet that comes closest to Aetrimonde in its orbit, Merimonde was the first planet that astronomers could view in any detail through their telescopes: it appears to consist mostly of ocean, with no ice caps and only a few, small islands, and is wracked by constant, continent-sized hurricanes. Some astronomers argue that the greenish tint to its oceans are a sign that Merimonde is home to plant life, at the very least.
  • Merimonde is associated with Deum Harmonious, god of nature. Originally this was due to its green coloration, but the association has been reinforced since the theory that it has plantlife became widely known. The transit of Merimonde is considered an especially auspicious time when it coincides with a solstice or equinox, already important dates in the worship of Deum Harmonious.
• Aetrimonde itself orbits fourth from the sun.
• Melamonde is a small and apparently frozen world orbiting far beyond Aetrimonde. Viewed through telescopes, it appears to be covered in ice or snow, with jagged peaks of black rock showing through.
  • Melamonde was unknown until the development of powerful telescopes, but it has come to be associated with Deum Untamed, the god of storms and trials. It has no historic association with festivals or folklore, but astrologers (not to be confused with astronomers) have started associating it with periods of hardship such as famines and floods.
• The final known planet in the system is recently discovered and not yet definitively named, for the measurements reported by the astronomers who discovered it were widely disbelieved. The sixth planet has a radius twelve times that of Aetrimonde, which was previously believed to be the largest object in the system. Like Nubrimonde, it is apparently covered in thick clouds (it is a gas giant, but Aetrimonde’s astronomers haven’t realized such a thing is possible yet), and is orbited by numerous moons, of which fourteen have so far been detected.
  • The unnamed sixth planet does not yet have a strong divine association. Astrologers have very recently started linking it with Deum Veiled, the god of secrets, for having escaped notice for so long.

Aetrimonde’s Moons

Aetrimonde itself has three moons:

• Nomis, the Constant, the White Moon, is the largest and typically closest of the three. (It is about 3.5 times the mass of Luna, Earth’s moon, but 30% further away, appearing about 15% larger in the sky). Aetrimonde’s lunar calendar is based on Nomis’ lunar cycle, which takes just over 35 days.
  • In Aetrimondean folklore, Nomis is associated with the virtues of steadfastness and loyalty, as its short lunar cycle and consistent size makes it a predictable presence in the night sky.
  • Nomis is generally associated with Deum Ruling, the god of laws, kings, and civilization, owing to its constancy as well as the fact that it is generally the largest celestial object in Aetrimonde’s sky.
  • Nomis is often cast as the narrator in classical dramas. In a common style of staging, the actor portraying Nomis moves gradually from one side of the stage to the other to symbolize the passage of time throughout the play, giving narration while in motion and remaining onstage but motionless during the action.
• Ubris, the Messenger, the Red Moon, is the smallest moon and has the second-closest orbit, but that orbit is eccentric, meaning that Ubris changes in visible size during its lunar cycle. At its closest approach, it appears about a quarter the size of Nomis. Ubris’ lunar cycle takes 191 days, more than half an Aetrimondean year.
  • Ubris is associated with wanderlust and deceit: its red light is bright enough, when it is close to Aetrimonde and Nomis is not in the sky, for thieves and scoundrels to ply their trade, while casting deep enough shadows for them to go unseen.
  • Ubris is sometimes associated with Deum Mocking, the god of trickery and defiance.
  • Folk belief would have it that actions taken under the red moon are subject to the whims of fate: they are unlikely to go exactly as planned, but may turn out for the better as a result.
  • In classical dramas, Ubris is often personified as a character hidden among the ensemble, who provides other characters with advice or objects that become important much later in the play. At that point, the actor portraying Ubris traditionally performs a dramatic reveal, shedding or reversing part of their costume to become clad in red.
• Exeris, the Stranger, the Black Moon, is the middle-sized of the three moons. It also has an extremely low albedo, and a highly eccentric orbit lasting more than three Aetrimondean years, making it all but invisible except when it is at its closest approach to Aetrimonde, when it passes just inside the orbit of Nomis and appears almost as large.
  • Exeris features in many myths as a harbinger of disaster (likely inspired by historical events discussed below).
  • When it has a divine association, it is with Deum Terminal, the god of endings and change.
  • According to a widespread folk belief, actions taken under the black moon will inevitably lead to disaster, and superstitious people try to remain indoors, doing nothing of import, when Exeris is in the night sky.
  • In classical dramas, Exeris is represented by a masked, silent player clad in black, whose presence in a scene indicates that the action on stage will, regardless of intentions, lead to tragedy.

Importantly, all three moons orbit Aetrimonde at angles to each other. Nomis and Ubris’ orbits are far enough from each other that they do not exert a significant gravitational pull on each other, but Exeris’ eccentric orbit passes near the other two, and means that it can, and has, come close enough to the other moons to disturb them. There is a close pass between Exeris and the other moons roughly every century, which normally affects their orbits just enough to require recalibrating some tide tables.

(Non-coplanar lunar orbits are possible in reality, but rare, and indicate a relatively young world. Over time, a planetary system with multiple moons would generally see the moons either crash into the planet, be slingshotted out of the system, or converge into a single orbital plane.)

However, the second-to-last close pass, which occurred just over a century ago, came close enough to Ubris that the resulting alteration to the Red Moon’s orbit was visible to the naked eye. This, in turn, significantly changed the pattern of the tides and altered some oceanic currents, resulting in a period of severe hurricanes and typhoons as the climate adjusted to its new equilibrium. The storms, thankfully, died down after a period of some ten years, but the events of the Stranger’s Message, as the close pass came to be known, inspired doomsday cults across Aetrimonde. Some believe that the resulting instability contributed to the outbreak of war during the Age of Steam.

Other Celestial Bodies

The Aetrimondean system is home to a number of other astronomical phenomena, including the Eye of Heaven, a toroidal nebula strongly resembling an eye, and the Herald of War, a red-tinted comet whose appearance in the night sky has preceded several major wars…probably by coincidence, but the astrologers claim otherwise.

Tides and Weather

With three moons in wildly different orbits, Aetrimonde has extremely rough seas, though they are becoming more navigable thanks to advances in shipbuilding, astronomy, and meteorology. In ages past it was only possible to sail the oceans because generations of sailors had charted safe routes through painstaking trial and error, and established sheltered harbors all along Aetrimonde’s coastlines.

The large mass of Nomis means that tidal forces are already relatively strong (about twice as strong as on Earth), but the presence of two other moons, and in non-coplanar orbits, make the tides far harder to predict, and can create freakishly strong tides at conjunctions where two moons line up closely with the sun over Aetrimonde. Under normal circumstances, astronomers can compute tide tables that are reasonably helpful up to a few months in advance, but when Ubris and Exeris pass close to Aetrimonde, their predictions become much less accurate (though the astronomers are getting better over time).

Aetrimonde has currents that are not driven by the tides, too, but they are weaker in comparison to tidal currents. Nomis’ tidal currents alone are strong enough that there are very few usefully consistent currents close to the coastline. (Aetrimonde has equivalents to Earth’s Gulf Stream and Antarctic Circumpolar Current, but close to shore, tidal currents are strong enough that they can weaken, cancel out, or redirect these permanent currents at various points in the lunar cycle.) When Ubris and Exeris form a conjunction with Nomis while passing close to the planet, their tidal forces added to Nomis’ can cause devastating tides, flooding coastal towns or completely draining shallow harbors.

Especially strong tides, such as those during a conjunction, are sometimes enough to bring together warm and cold currents that wouldn’t otherwise meet. This, in turn, causes hurricanes and typhoons that regularly batter coastal areas. Aetrimonde’s meteorologists are only just figuring out how to predict these events: historically, the first sign of an unseasonal storm would be a cloud on the horizon, at which point it was often too late for a ship to find safe harbor. Today, perhaps one in five major storms can be predicted a few days in advance, giving sailors enough advance warning that they can remain in port while it passes…or try to outrun it, if they feel like taking the risk.

To make all these matters worse, when Exeris makes a close pass with one of the other moons it causes changes to the orbits of both, which requires astronomers and meteorologists alike to recalibrate their models and leaves the tides and weather unpredictable for as much as a year at a time. The Stranger’s Message was particularly bad in this respect, and it took the better part of a decade for seafaring to become as safe as it had been before the Message.

In short, Aetrimonde’s seas are incredibly dangerous, and not just to ships at sea; coastal regions have to be rebuilt on the regular, and port cities have to be carefully planned to deal with the occasional freak tide. Most ocean-going ships stick close to shore whenever possible, because the risk of a freak storm is such that captains prefer never to be more than a day’s sailing from a safe harbor. Blue-water exploration is a fool’s errand in Aetrimonde, and although astronomers and cartographers are confident that Aetrimonde is far larger than what they have explored and mapped, there is no real effort to find out what lies beyond the edges of the map.

Sea Magic

Because of all the dangers associated with the oceans, ship captains hire “sea witches” whenever possible. These are people with some magic making seafaring less dangerous, whether that be outright control of the weather, the ability to predict storms and currents ahead of time, or a divine blessing that ensures a ship will survive rough seas. Some of these people are trained arcanists or anointed priests with other magic to their names, but many just have the one trick letting them sail the oceans without fear.

Other Tidal Effects

Aetrimonde’s stronger tidal forces are most apparent in the tides and weather, but the moons’ gravity affects the entire planet and everything on it. Avalanches, landslides, and earthquakes occur more often during conjunctions of the moons, and Aetrimonde’s few volcanoes become more active during these periods as well. Mines are known to shut down operations during a close pass (if the owners have any care for the workers) as a precaution against collapses, and many nations have laws mandating structural inspections of large buildings following a conjunction.

The Calendar

Aetrimonde’s solar year is 353.14 days long. The Novan calendar, which is the most widely-used in Aetrimonde, observes a year of 353 days, divided into ten months of 35 days each (matching Nomis’ lunar cycle) with the leftover three days making up a short intercalary month around the winter solstice. Every seven years, the intercalary month is extended by one day, to account for the extra 0.14 days in the solar year.

The months of the Novan calendar are the unimaginatively named Primus, Secundus, Tertius, Quartus, Quintus, Sextus, Septus, Octus, Novus, and Decus. The intercalary month, which occurs between Decus and Primus and is generally celebrated as a holiday, is named Festus.

Each month is divided into five weeks of seven days. The names of the days of the week are taken from the old Auran calendar, in which they were associated with the seven gods with the most prestige and power in the old Auran Empire. They are (in order of the associated god’s ascending importance) Luxens, Scirens, Facens, Pugnens, Virtens, Concordens, and Imperens. The days of the intercalary month are considered to be outside of the normal cycle of months and weeks, and are not assigned a day of the week: every month and year thus begins on Luxens and ends on Imperens.

In the Auran Empire, Imperens was a day given over to religious services and civic duties, and people generally worked the other six. The use of Imperens for religious observations persisted after the Collapse, and spread wherever the Auran calendar was adopted. Recently, labor reforms originating in Waystone have turned Concordens into a second day of rest, although this has not yet spread to the rest of the world.

The Seasons

Aetrimonde has an axial tilt just slightly greater than Earth’s, making it experience slightly more severe seasons (though they are also slightly shorter, owing to the shorter year). In the Auran calendar, the seasons are defined to be:

• Spring from 10 Secundus to 27 Quartus, with the equinox occurring on 17 Tertius.
• Summer from 28 Quartus to 9 Septus, with the solstice occurring on 1 Sextus.
• Autumn from 10 Septus to 27 Novus, with the equinox occurring on 19 Octus.
• Winter from 28 Novus to 9 Secundus, with the solstice occurring on 2 Festus.

Days, Hours and Minutes

I preface this section on Aetrimondean timekeeping by saying that I only include it in the interest of worldbuilding, and I strongly recommend that a GM only use it if the players at the table are heavily into roleplaying and want the extra immersion. Otherwise, just pretend that Aetrimonde somehow independently invented the same system of hours and minutes that Earth did.

The Aetrimondean solar day is almost exactly as long as Earth’s day. Before the invention of accurate timepieces, it was customary to divide the time between dawn and sunset into ten roughly equal hours, and the same for the time between sunset and the next dawn. In the summer, hours would be longer during the day than during the night, and the opposite would be true in the winter, but since nobody could accurately measure time this was not too awful a problem.

As clocks became reasonably widespread, the world largely adopted a system of timekeeping based on the one invented and imposed by the bureaucrats of the Novan Imperium. This system divides the day into twenty hours (ten each in the morning and the evening) of a hundred minutes, with each minute being further divided into a hundred seconds. An Aetrimondean minute is thus only about 72% as long as an Earth minute, or about 43 Earth seconds.

The Novan bureaucracy, as may be becoming apparent, very much likes being able to decimalize, or divide things into ten parts. They originally lobbied for there to be only ten hours in the day, but were overruled by the Novan Emperor of the time, who objected to the idea on the grounds that a tenth of a day was far too long a period of time to be useful. (His exact words are reported, perhaps apocryphally, to have been “Once you have doubled the length of the hour, will you then halve the hours of our meetings? I think not.”)

Campaign Hooks

Aetrimonde’s unusual planetary system offers several oddities that could be the foundation for an entire high-concept campaign:

• A wealthy and eccentric shipbuilder has financed the construction of a vessel that can survive the open seas, in order to fulfill his dream of exploring those parts of Aetrimonde more than a few days beyond a safe harbor. The PCs have been recruited as part of the ship’s company; what strange new lands and new civilizations will they discover?
• Aetrimonde’s astronomers have come to a dreadful conclusion: the Stranger’s Message has put Exeris in a new orbit that will see the Black Moon collide with Nomis within a few short years. The resulting shower of orbital debris will most likely wipe out all life on Aetrimonde. The only hope of averting this lies in recovering and repurposing a variety of artifacts and major rituals, like Orcimedes’ Lever and the Dread Spell of Eternal Night, to readjust the lunar orbits into a more stable configuration.
• Cosmologists have for some time now claimed that Aetrimonde is an unnatural planet, pointing to “anomalies” like the misaligned lunar orbits as evidence that Aetrimonde is a far younger world than the rest of the planets in the system–too young, they say, to support life. Since Aetrimonde self-evidently has life on it, they have mostly been laughed at. But now, a team of applied cosmothaumatologists have measured intense concentrations of magical activity spread throughout inaccessible regions of Aetrimonde: deep beneath the seas, buried at the edge of the planet’s molten mantle, and even on the far sides of the moons. They believe these loci are actively maintaining Aetrimonde as a habitable world, and are planning an expedition to the most accessible one. Is Aetrimonde an artificial world? If so, what created it? And should mortals really be messing about with whatever keeps their world habitable?