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Hollow Moon Planetology: Blue Moon -- Eclipsesby Sharon Dornhoff
Out-Of-Turn Disasters: Eclipses in the Hollow Moon
Consulting the HM calendar, you can see that Materans are faced with severe geological upheavals every nine months, moderate to mild ones roughly every three months, and one or two Storm Times in any given month-long period. (While this may seem like too little precipitation for those regions which receive rainfall only during a Storm Time, remember that in the absence of direct sunlight very little of this moisture is lost, to evaporation or to the transpiration of plant life.) Superior "growing seasons" occur at times when rainfall takes place early in the hours of greater illumination -- the 6th to 9th and 15th to 18th months, especially -- but agriculture in general is a year-round enterprise. Evacuations to safe ground are planned well in advance, for communities imperilled at Fire Time, and weather patterns are well-understood by sea- sailors, windship-crews and iceriggers; indeed, cryions depend upon the unchanging regularity of circle tides for their biannual migrations. The lunar year is orderly, familiar, and trustworthy.
Except, unfortunately, for the Doom Times; that's when their whole, meticulous system of disaster-prediction goes to pot. Doom Times are disasters that break the pattern ... that occur without any warning ... that can strike at any moment, during "fulldark", and make even the mighty crystalbarrens tremble beneath Materans' feet. Even the brilliant cosmologists of L'mor in the kopru empire, or the soothsaying fractrologer- sages of Cynidicea, can't predict anything more specific than whether a Doom Time MIGHT occur, in a given month; conventional magics, which allow lunar spellcasters to easily predict gravity-induced disasters, are powerless to anticipate these rogue catastrophes.
In a way, the fact that Materans weather so many predictable, recurrent cataclysms -- so often and so frequently, they become routine -- makes these erratic demonstrations of nature's fury even MORE frightening, for lunar folk: they've seen, time and time again, the shattered ruin that disasters have made of their evacuated lands, upon their return; and the prospect of being at ground zero, with no time to run, when such destructive power is unleashed scares them spitless! But more than that, such disasters run counter to the way Materans expect the world to work -- they're rare enough, that lunar natural theology doesn't have a place for them -- and leave them thinking they must've somehow sinned against their patron Immortals, to have invited such "abnormal" misfortunes upon themselves. Doom Times upset moon-natives as something "against nature" -- a change in the very structure of their otherwise-orderly universe -- the same way you or I would be rattled if the sun rose in the morning, then changed its mind and sank back below the eastern horizon. It might be easier to for them bear, if only they knew WHY the Immortals see fit to unleash such devastation upon them, but they don't.
They can't. Most Hollow Moon natives (it's about time I mentioned this) don't know they're living inside of the moon, any more than Hollow World natives know they're inside Mystara. Races that deliberately immigrated across space (i.e. gnomes and Nephthisians) are an obvious exception, but their views are dismissed as nonsense by the vast majority of lunar cultures; everyone else "knows" -- assuming their culture has any recollection of their Mystaran origins, at all -- that "the moon" was a flat disk in the sky, certainly not a sphere (!), and probably only a few miles across. The Hollow Moon, as far as its natives are concerned, is a universe unto itself, with nothing beneath the crystal but more crystal. Mare Orientale is a doorway to some terrible other plane that's guarded by fiendish creatures: a realm of whispered legendary* from which pathetic and half-mad refugees have been known to emerge, but which plays no part in Materan lives or cosmology. The "sunlight" that penetrates the Farside IS the sun, to Materans: it's the Firmament, ITSELF, that's glowing, not some mythical, globe-shaped external light source! Even the Storm and Fire Times occur when they do, because the Immortals will it that way ... not because of gravity from some unseen (indeed, unseeable) sister-satellite they've never heard of. While this cosmology works perfectly well, for them -- HAS worked, in fact, for longer than the Hollow World's "Immortals changed the world for us!" concept has held up -- it utterly confounds any attempt to predict the coming of Doom Times, let alone to understand why such events truly take place.
(* - Materans think of this "Realm of Peril" beyond Mare Orientale the same way Cerilians in the Birthright setting think of the Shadow World; they tell horror stories about it, none of which even come close to the truth. Visitors from Mystara who mention their origins to friendly Materans will, in all probability, be consoled by their hosts for the "terrors" they have surely endured, and patronisingly reassured that it's okay: they're safe now. :-))
"Doom Times" are worldwide lunar earthquakes which are induced by Materan total eclipses. Solar eclipses don't do a darn thing, to Matera -- they happen when the moon's shadow strikes Mystara, not vice versa -- and Patera's tiny size and light-bending properties make the effect of Patera- induced eclipses upon the larger moon negligible. But when Mystara's shadow cuts off the sunlight from Matera's illuminated outer surface, the resulting drastic temperature-shift is so extreme and sudden (from 210 F to -240 F in a matter of seconds*, then back again when the eclipse abates), it actually causes the outermost layer of the crystalline bedrock to shrink from the cold, then expand back to its original size. The actual size- change is minute, if measured against the vastness of Matera as a whole, but it's still enough to "squeeze" the inner moon ... an abrupt, global contraction that causes tremors even on the open crystalbarrens, where the ground is normally stable and the volcanoes are all long-dead. A brief eclipse of less than half an hour might induce a 4.0 quake at its beginning and a 5.5 at its end, with longer-term geological repercussions if it sets off a volcanic eruption or flood; the longest Materan total eclipse possible, which lasts about 2 3/4 hours**, can bring about convulsions of 7.0 at the start and a whopping 9.5 at the end, with minor tremors (3.0 or less) continuously occurring throughout the interim. Doom Times always consist of two major quakes, the first (when the surface temperature plummets) less powerful than the second (when it rises again), with lesser quakes in between during the longest-lasting eclipses. The worst of all are those few -- thankfully, a tiny minority -- that strike at the same time as a regularly-occurring Fire Time; such flukes happen only once every four or five (Mystaran) centuries, but can lay waste to entire cultures, should they set off eruptions of otherwise-quiescent volcanoes that weren't SUPPOSED to come to life that month. At the same time, Matera's inner atmosphere goes berserk from the sudden shifts in air-pressure, producing violent, out- of-season thunderstorms and roaring winds bearing no relation to normal weather-patterns of the HM setting. This added chaos in the skies, in combination with the shuddering ground felt all over the globe (!), is more than enough to give the uninitiated an overwhelming impression that the world, itself, is coming to an end.
(* - This is true. Sensors on Luna have recorded such rapid changes in surface temperature for total (umbral) lunar eclipses; penumbral eclipses and lunar "appulses" (partial penumbral eclipses) have a lesser effect.)
(** - IRL eclipses can take up to 3 hours and 40 minutes to occur, with true "totality" lasting up to an hour and 40 minutes. Mystara is smaller than Earth, however, so its shadow will block Matera's surface from the sun for only 3/4 as long, on any given eclipse.)
Eclipses IRL happen in accordance with what is called the "saros cycle", a 223-lunation (lunar month) pattern that determines when an eclipse of the sun or moon will be visible from a given location on the Earth. Materan "Doom Times" occur a lot more often than this, as the Hollow Moon gets squeezed by total eclipses, no matter WHERE they are visible from the planetary surface! Lunar eclipses and appulses can take place from zero to three times per (Mystaran) year, and follow a regular pattern such that there's a 37 1/2-day "eclipse season" every 173 days. Lunar eclipses, by their very nature, can only occur during a full moon; any full moon that takes place during the eclipse season's "window of opportunity" may experience such an event, although not all will do so. About 1/3 of lunar eclipses are total; luckily, only total eclipses cause enough of a temperature-shift to induce earthquakes in the HM setting. There are exactly 150 lunar eclipses -- total, penumbral, and partial/appulse -- per Mystaran century.
Timing of Materan Eclipses
There's three ways I can think of to keep track of eclipses, for a long- term HM campaign. (For a short-term visit by Mystaran PCs, of course, it's not really necessary; there can be a Doom Time if the adventure calls for it, after which the PCs probably won't be there to count off the time until the next one. But one of the virtues of the Mystara setting has always been the IMPRESSION, if not the reality, that it conforms to real-life cultural and physical principles -- What other game-world has a table of when the moon rises and sets, even if it's totally bogus...? -- and I'd like to continue in that tradition, so bear with me. :-D) If you'd like to use a Doom Time as a plot device, the first method should work just fine; otherwise, assuming you've got web-access -- which you must, if you're reading this! -- pick whichever of the other two methods you think is best for you.
1) Pick a month, any month. Have a Doom Time occur then, at a randomly-determined time during the 56 hours of fulldark. Allow a 1-in-3 chance that there will be another eclipse -- total or otherwise -- the next month. Additional eclipses, or pairs of eclipses, will then have a 50% chance of occurring every 173 days. Note that an eclipse is only total about 1/3 of the time, so not all of the ones you roll up will produce a Doom Time ... which is another reason Materans have so little ability to predict these disasters.
2) Pick an IRL year, any IRL year. Check out the Web's various astronomy sites, several of which include predictions for future eclipses and/or records of when they've fallen in the past; or look up world-wide lunar eclipse records, at your local library. Starting at the Mystaran New Year, schedule the IRL year's lunar eclipses accordingly (Felmont becomes June, Fyrmont becomes July, etc); then transfer them over to the Materan calendar, via the moon-phase charts TSR has so-thoughtfully provided. If an IRL eclipse falls on a night that's not a full moon on the Mystaran calendar, move it to the nearest full-moon night -- your players need never know ;-D. If it falls on the 29th, 30th, or 31st of a month, ignore it -- Mystara's smaller than Earth, so a certain number of eclipses that would result from Earth's larger shadow will miss Matera entirely.
3) Do the same thing as above, but -- for a nice touch of parallelism - - use a table of eclipse-records for the very year (AD => AC) which you're playing out, in your own game-sessions! Materans may not know how to predict lunar eclipses, but astronomers IRL have calculated exactly when they must have taken place, for all of recorded history. There's a certain appeal in being able to use Mystara's regular, unmodified calendar, not only to look up current or coming eclipses, but to leaf back through the centuries and say that such-and-such a devastating Doom Time happened RIGHT THEN, on such-and-such a date, year so-and-so BC! And as a fringe benefit, you can even start reporting solar or lunar eclipses to PCs on Mystara, by picking an IRL location that corresponds to, say, Thyatis in its latitude, and noting when a solar or lunar eclipse would be visible from that region.
Materan lunar eclipses last 3/4 as long as their Earth/Luna equivalents, and are of identical type (total, penumbral, partial/appulse) to those listed in IRL charts of such events. Frankly, I doubt if Materan eclipses would actually follow the same saros cycle as Luna, given the difference in their orbital periods and in Mystara compared to Earth; but using IRL patterns will keep things nice and unpredictable for HM cultures, with Doom Times happening three times in every two 18-month years on average, yet with an enormous variability that allows for none in some years, and up to six (!) in others*. Remember that an eclipse can NEVER occur, except on the night of the full moon -- that's the only time Mystara is between Matera and the sun, to block the light -- so even if you'd rather not bother with any of these methods and just have a Doom Time whenever you feel like it, be sure that they only happen when it's physically possible.
(* - Such anomalies, either of no Doom Times or of multiple repeated ones, become legendary to HM cultures, and are respectively recorded by historians as times of great Immortal generosity or wrath; some HM cultures even count off the years, not from the crowning of a leader or their arrival on Matera, but from a particularly-bad Doom Time or an unusually-long period of geological quiet.)
The worst Doom Time on record happened some twelve (Mystaran) centuries ago, striking simultaneously with the severe Fire Time between the 9th and 10th months/lunar "days", and devastating virtually all then- extant Materan civilisations. The ruins which it and other Doom Times have left scattered throughout the Hollow Moon provide a handy focus for adventures, exploration, or archaeological investigations.