Hollow Moon Planetology: Blue Moon -- Eclipses
by 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.