Mapping Issues: Axial Tilt

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Mapping Issues: Axial Tilt

Postby Thorf » Wed Mar 28, 2012 2:40 pm

Issue Resolved: arbitrary axial tilt of 24 degrees adopted.

  • Large volume of evidence for there being a tilt (seasons, explicit references in the timeline, etc).
  • No official source defines the axial tilt.
  • Similarity to real world earth suggests adoption of similar axial tilt.
  • Real world axial tilt is not stable but varies between roughly 22-24.5 degrees.
  • Most arctic and antarctic areas of Mystara fall within polar openings.
  • Polar lip likely begins between 62 and 66 degrees.
  • It seems preferable to have the arctic circles before the polar lips begin.

Therefore the Atlas has settled on an axial tilt of 24 degrees. This places the arctic circles at 66 degrees, which is the exact point where the polar lips start according to current theories.

(Original discussion follows...)


Has anyone found an official reference giving the value of the axial tilt of Mystara?

In the past I know we've discussed this, and concluded that for a whole host of reasons having an axial tilt similar to (or the same as) earth's is the best solution. But I'm wondering what the official stance was, if any.

The only source I've been able to find so far is the Precataclysmic Outer World Map, which marks the postcataclysmic equator in relation to the equator. I measured it in Illustrator and got a result of 37.4-37.7 degrees. It's not a precise calculation.

The earth's axial tilt is 23.44 degrees, which is much shallower. I have to wonder what effect this would have on seasons, weather patterns, and so on. It certainly would be a lot simpler to have a tilt the same as earth's.
Last edited by Thorf on Sat Feb 23, 2013 4:07 am, edited 2 times in total.
Reason: Added summary and resolution.
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Re: Mapping Issues: Axial Tilt

Postby Seer of Yhog » Wed Mar 28, 2012 2:51 pm

This is a very good question. I did a quick search and I came up with this article by LoZompatore, which assumes the same tilt as Earth but does present some implications of such a tilt (namely, that light from the sun would filter through the polar openings for at least part of the year).
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Re: Mapping Issues: Axial Tilt

Postby Zendrolion » Wed Mar 28, 2012 4:46 pm

Seer of Yhog wrote:I did a quick search and I came up with this article by LoZompatore, which assumes the same tilt as Earth but does present some implications of such a tilt (namely, that light from the sun would filter through the polar openings for at least part of the year).


Yeah, I remember LoZompatore posting that on the Italian MMB years ago, it was a very appreciated article. As far as we researched, nowhere Mystara's axial tilt is given in canon sources. I'd assume it to be roughly the same of Earth (around 23,5°) even if - as Geoff pointed - this would have major consequences on the Darklands area as they've been described. In fact, they'll be no more Darklands, but only a small part of Mystara's torus region would never receive sunlight both from the HW sun and from the OW sun; in other areas of the "Darklands" you would be able to see even both suns at once!

Nevertheless, in my opinion this seems to be the most viable solution: changing the Darklands a little. To preserve the Darklands as they're in canon sources, you'd need a zero-degrees axial tilt, which would cause the absence of seasons - a much greater change that will affect many setting details (seasonal festivals, calendars, changing weather, and so on).
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Re: Mapping Issues: Axial Tilt

Postby Hugin » Wed Mar 28, 2012 5:47 pm

The outer world map in the HW set shows the tropics being at very near the 23° mark. Since the tropics are defined by the planetary tilt, I'd say it's quite official in its approximation, even if it doesn't come right out and say precisely 23.44°. I'd just use the approximate 23.5° myself as being close enough for usable purposes.
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Re: Mapping Issues: Axial Tilt

Postby Thorf » Wed Mar 28, 2012 6:07 pm

You set me off, Geoff. It's my own fault for asking the question. :mrgreen: Now three hours later...

Sunlight with an Axial Tilt of 23.44 degrees, the same as earth
ImageImage

Sunlight with an Axial Tilt of 37.5 degrees, as marked on the Precataclysmic Map
ImageImage

I'm definitely liking the first option - 37.5 degrees just seems like too much of a tilt.

Note that the world dimensions used here for Mystara are based on the ongoing analysis of hex maps overlaid on world maps in the World Dimensions and Sorting out the Outer World threads.

In any case, it looks like there are indeed darklands, in an uneven circle around the pole.
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Re: Mapping Issues: Axial Tilt

Postby Ashtagon » Wed Mar 28, 2012 6:22 pm

Well, the pre-cataclysmic maps and comparing equator lines pre and post-cataclysm aren't really a guide in this case -- the cataclysm canonically did cause the world to change its axis after all. It is quite possible that the planet had different axial tilts pre and post cataclysm.

Aren't the tropics of M-Cancer and M-Capricorn marked on some of the maps? That, by definition, is a canonical answer to this question. If we have M-Arctic and/or M-Antarctic circles marked, that too would answer this question conclusively..
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Re: Mapping Issues: Axial Tilt

Postby Thorf » Wed Mar 28, 2012 6:35 pm

Ashtagon wrote:Well, the pre-cataclysmic maps and comparing equator lines pre and post-cataclysm aren't really a guide in this case -- the cataclysm canonically did cause the world to change its axis after all. It is quite possible that the planet had different axial tilts pre and post cataclysm.


Good point, Ash.

Aren't the tropics of M-Cancer and M-Capricorn marked on some of the maps? That, by definition, is a canonical answer to this question. If we have M-Arctic and/or M-Antarctic circles marked, that too would answer this question conclusively..


Hehe, yes - the Hollow World maps all show tropics and arctic/antarctic circles, even the Precataclysmic map.

And they all show them at the same levels. In other words, going by the tropics, the axial tilt didn't change at all.

At this point I'm pretty sure the Atlas will be going with 23.44 degrees.
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Re: Mapping Issues: Axial Tilt

Postby Birchbeer » Wed Mar 28, 2012 6:41 pm

Not to add in additional complexity, but the Earth's axial tilt occasionally shifts normally as well. Per Wikipedia:
Over the last 5 million years, the obliquity of the ecliptic (or more accurately, the obliquity of the Equator on the moving ecliptic of date) has varied from 22.0425° to 24.5044°, but for the next one million years, the range will be only from 22.2289° to 24.3472°

1ish degree isn't too much I think. I'm tossing this out there just so we can account for it if needed.
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Re: Mapping Issues: Axial Tilt

Postby Thorf » Wed Mar 28, 2012 7:08 pm

Birchbeer wrote:Not to add in additional complexity, but the Earth's axial tilt occasionally shifts normally as well. Per Wikipedia:
Over the last 5 million years, the obliquity of the ecliptic (or more accurately, the obliquity of the Equator on the moving ecliptic of date) has varied from 22.0425° to 24.5044°, but for the next one million years, the range will be only from 22.2289° to 24.3472°

1ish degree isn't too much I think. I'm tossing this out there just so we can account for it if needed.


I just read the exact same thing. So what this means is that we can choose a figure around about there and stick with it. :D

Any preferences? I'm partial to 23.5 myself. 24 is nice and regular, but with figures like this I think it actually sounds better (more realistic!) to have less round figures.
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Re: Mapping Issues: Axial Tilt

Postby Hugin » Wed Mar 28, 2012 7:29 pm

Thorf wrote:I just read the exact same thing. So what this means is that we can choose a figure around about there and stick with it. :D

Any preferences? I'm partial to 23.5 myself. 24 is nice and regular, but with figures like this I think it actually sounds better (more realistic!) to have less round figures.

I'll be going with 23.5° as well. And really nice diagrams above!
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Re: Mapping Issues: Axial Tilt

Postby Ambreville » Wed Mar 28, 2012 9:34 pm

One might wonder what the effect of conflicting gravity/gravities might be near the polar openings. HW gravity pushes outward. Outer World gravity draws inward. Therefore, there could be a spot in mid air where gravity is equal to zero. Isn't it so? Gravity on the surface, including the lip, would however remain constant. Shaping the space where gravity is nullified could be interesting (is there an astrophysicist aboard?)
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Re: Mapping Issues: Axial Tilt

Postby Gecko » Thu Mar 29, 2012 12:01 am

Ambreville wrote:One might wonder what the effect of conflicting gravity/gravities might be near the polar openings. HW gravity pushes outward. Outer World gravity draws inward. Therefore, there could be a spot in mid air where gravity is equal to zero. Isn't it so? Gravity on the surface, including the lip, would however remain constant. Shaping the space where gravity is nullified could be interesting (is there an astrophysicist aboard?)


hmm... Trying to picture it through- It seems like Right in the middle of the medianic circle there would be a Lagrange-type spot of effectively micro-gravity. If you could somehow place something there and kill all it's inertia & momentum other than to put it matching that of the planets revolution, it could stay suspended there for a very long time, though eventually the gravity from the world shield regions of the opposite pole, and of more equatorial regions, would eventually pull it into the hollow world proper... At least, I would think... (and that's assuming the world shield rock is uniform in the polar regions with the rest the planet)
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Re: Mapping Issues: Axial Tilt

Postby Thorf » Thu Mar 29, 2012 5:30 am

I've changed my mind. It turns out that 24 is perhaps a better choice, because it's a valid earth equivalent and it means that the arctic circle starts at 66 degrees. If the tilt is 23.5, the arctic circle is at 66.5. That's not necessarily a bad thing, but it would be nice to have the arctic circle starting as far south as possible.

In any case, the exact number chosen in the end will be arbitrary. There's no way around that.

Since this discussion seems to have come to a reasonably solid conclusion, I'm going to go back to the World Dimensions thread for the continuation of this discussion. If anyone has any more comments or ideas on axial tilt, or an argument for adopting something other than 24 degrees, feel free to continue discussing that here.
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Re: Mapping Issues: Axial Tilt

Postby Big Mac » Thu Mar 29, 2012 2:01 pm

Great thred, Thof! :cool:

Seer of Yhog wrote:This is a very good question. I did a quick search and I came up with this article by LoZompatore, which assumes the same tilt as Earth but does present some implications of such a tilt (namely, that light from the sun would filter through the polar openings for at least part of the year).


Hmm. This phenomenon could be percieved by the Hollow Worlders as being something similar to the Northern Lights/Southern Lights in the real-world. They might not even realise there is another sun out there. Sages might think it is something to do with their own sun and some sort of force that bounces light back.

Ashtagon wrote:Well, the pre-cataclysmic maps and comparing equator lines pre and post-cataclysm aren't really a guide in this case -- the cataclysm canonically did cause the world to change its axis after all. It is quite possible that the planet had different axial tilts pre and post cataclysm.

Aren't the tropics of M-Cancer and M-Capricorn marked on some of the maps? That, by definition, is a canonical answer to this question. If we have M-Arctic and/or M-Antarctic circles marked, that too would answer this question conclusively..


Unless the world flipped over 180 degrees, I would agree that you would need to have two different tilts.

Do you (or anyone else) have the exact quote from the stuff about the cataclysm? Perhaps we can infer if the cataclysm made the tilt larger or smaller.

Thorf wrote:Hehe, yes - the Hollow World maps all show tropics and arctic/antarctic circles, even the Precataclysmic map.

And they all show them at the same levels. In other words, going by the tropics, the axial tilt didn't change at all.

At this point I'm pretty sure the Atlas will be going with 23.44 degrees.


That would seem to be an error (no offense to the designers intended). I think the thing with the fantasy worlds that TSR created is that some of them are such epic concepts (including the idea of a Hollow World) that you could probably do a degree-level of study in how the fantasy rules of nature would affect the people living on those worlds. I don't think that designers have the time to flesh out all the really wacky ideas to the nth degree. In a way I think that the more vanilla campaign settings are slightly easier to deal with, as you can use real-world assumptions about things like the effects of the moon on tides.

Ambreville wrote:One might wonder what the effect of conflicting gravity/gravities might be near the polar openings. HW gravity pushes outward. Outer World gravity draws inward. Therefore, there could be a spot in mid air where gravity is equal to zero. Isn't it so? Gravity on the surface, including the lip, would however remain constant. Shaping the space where gravity is nullified could be interesting (is there an astrophysicist aboard?)


I know a lot less about "Heardian laws of nature" than "Grubbian laws of nature", but I would concur that you would get a zone (actually a sphere - or a distorted sphere) where internal and external gravity would balance.

Within the world, that zone would probably have super high pressure (from the weight of both the internal and external continents).

In the Polar Openings, it could be a zero gravity zone. But that really depends on how gravity fits the surface of the world. If gravity is "ground hugging" it could just "bend" around the curvature of the openings and allow a person to walk through the Polar Openings. If that was the case (and I don't have the sources to check) you might instead get a line of zero gravity that went through the middle of both Polar Openings (and the internal sun).

I think that either way would be a valid way to design the world's gravity.
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Re: Mapping Issues: Axial Tilt

Postby Carillion » Fri Mar 30, 2012 8:07 pm

But I'm wondering what the official stance was, if any.


The Dungeon Master's Sourcebook for the Hollow World has a diagram on page 21 which shows a cross section of Mystara. This diagram shows the permanent dark areas around each pole, which could only be achieved if there was no axial tilt at all.

As having no axial tilt would cause all sorts of problems, and as it does not specifically state that there is no axial tilt, I think this should be considered an error in the diagram.

I just thought I would mention this, as someone may raise it as an objection at a later date!
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Re: Mapping Issues: Axial Tilt

Postby Thorf » Sat Feb 23, 2013 4:10 am

I just added the following to the first post of this thread;

Issue Resolved: arbitrary axial tilt of 24 degrees adopted.

  • Large volume of evidence for there being a tilt (seasons, explicit references in the timeline, etc).
  • No official source defines the axial tilt.
  • Similarity to real world earth suggests adoption of similar axial tilt.
  • Real world axial tilt is not stable but varies between roughly 22-24.5 degrees.
  • Most arctic and antarctic areas of Mystara fall within polar openings.
  • Polar lip likely begins between 62 and 66 degrees.
  • It seems preferable to have the arctic circles before the polar lips begin.

Therefore the Atlas has settled on an axial tilt of 24 degrees. This places the arctic circles at 66 degrees, which is the exact point where the polar lips start according to current theories.


Any objections or further points? I'm planning on adding similar summaries and resolutions to the other Mapping Issues threads, because I'm getting fed up of coming back to this after some time and having to read through the entire discussion to remember everything.
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Re: Mapping Issues: Axial Tilt

Postby Morfie » Sat Feb 23, 2013 5:54 am

Any masochistic DM working out a calendar for Myoshima should be aware that Mystara has no axial tilt, unlike many worlds (including Earth). All references to Mystara having any sort of tilt are erroneous, and such references in Dragon Magazine issue #160 and the Champions of Mystara® boxed set should be corrected.


Polyhedron 120, Page 23. Article by Roger E Moore.

I have only just read this for the first time yesterday, thanks to the Internet Archive.
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Re: Mapping Issues: Axial Tilt

Postby Thorf » Sat Feb 23, 2013 9:20 am

Morfie wrote:
Any masochistic DM working out a calendar for Myoshima should be aware that Mystara has no axial tilt, unlike many worlds (including Earth). All references to Mystara having any sort of tilt are erroneous, and such references in Dragon Magazine issue #160 and the Champions of Mystara® boxed set should be corrected.


Polyhedron 120, Page 23. Article by Roger E Moore.

I have only just read this for the first time yesterday, thanks to the Internet Archive.


Interesting article, which I hadn't heard of before, but that part of it is revisionism of the worst sort. I'm trying to remember what credentials Roger E Moore has as a Mystara author... All that comes to mind is notes on the AD&D conversion of GAZ13 (which really didn't amount to anything that wasn't already there), and proofreading on Karameikos: Kingdom of Adventure. That's not a lot. Then there was the Chronomancy article, which was also mainly about conversion.

The bottom line: I think we can safely ignore Roger Moore's opinion in this case, regardless of his official position.
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Re: Mapping Issues: Axial Tilt

Postby Morfie » Sat Feb 23, 2013 9:52 pm

If we used this article as canon, it would raise even more issues that would have to be solved.

No axial tilt, means no seasonal weather -> Unless the planet has an orbital eccentricity on the level of Mercury -> This creates seasons, but they are the same on different hemispheres.
Not this matters much, since Mystara has had very little development below the equator.

Mystara is supposed to be Earth-like, after all. We have enough issues with the Hollow World openings without changing anything else..

The article also doesn't say why there is no axial tilt.

Also the article was written in 1996 after Mystara was dropped, so we can safely ignore it ;)
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