Yelm Eclipsed

[1d8+DB]

So, does Glorantha  have solar eclipses; and what is the mythic explanation of these events?   Orlanth periodically humiliating Yelm?  A persisting ancient magic of the Elder Races?   The Red  Goddess  trying to seduce Yelm?

[Joerg]

Eclipses in Glorantha are somewhat problematic because normal geometry like triangulation doesn't quite work.

Theoretically, there ought to be a daily eclipse where the sun is hidden by the Red Moon, but it isn't clear where on the surface world this shadow would fall. It is possible that such an effect could occur in the northernmost bits of the earth square, or in the far distant north on Sramak's River.

But then it isn't clear whether the Red Moon is big enough to cause more than a partial eclipse. Its apparent diameter and height are magical effects, with the Glowline interfering.

It isn't entirely clear whether the diameter of the sun is constant over the year - the winter sun may be smaller or more distant than the summer sun. The Sunpath certainly tilts north and south, causing a more southerly eclipse belt in summer.

 

There is a strange stellar body known for causing eclipses of lesser stellar bodies, the juggernaut. Again, it isn't clear whether it is big enough to blot out the sun.

 

There is a myth about Telmor devouring the sun. Is there something like a stellar wolf?

[David Scott]

I would suggest that the Red Moon never eclipses the Sun. To do so would be a challenge to the Solar supremacy that the Lunar religion parallels. It's happened in the Godtime, once the perfect sky was disturbed. Maybe at sunstop as a great shadow passed across the sun before it started again. 

[davecake]

There is clearly at least a time and place where the moon blocks the sun. But that place might normally be inside the Crater at noonwhen Yelm is overhead, which is not a place that is normally accessible or hospitable to humans. I don't think there is otherwise a time it happens in other parts of the world. 

Yelmic mythology acknowledges that Yelm has a shadow, a place he cannot see. The black fire that is Yelm shadow is there, and Kazkurtum nourishes it. When there is an eclipse, this would be the world. 

[Revilo Divad Of Dyoll]

Could there also be moments when, as the Blue Moon falls into Magasta's pool, it momentarily blocks the Sun (at least from certain angles)?

[1d8+DB]

So, there would be nothing  like this world's periodic, predictable eclipses: if  a shadow crosses the face of the sun on Glorantha it is a singular apocalyptic event that would probably signal vast and cosmic upheavals.

[Darius West]

Given that Yelm moves over the world in a pre-described circular trajectory and the Red Moon is fixed over Peloria, well away from that arc, by my calculations you would need to be standing in Spol near dusk to see the Red Moon eclipse Yelm and it would be a daily affair, happening in the late afternoon.  Spol is, after all, a land of darkness worship within the Lunar Empire, and now you know why...

[Joerg]

3 hours ago, Darius West said:

Given that Yelm moves over the world in a pre-described circular trajectory and the Red Moon is fixed over Peloria, well away from that arc, by my calculations you would need to be standing in Spol near dusk to see the Red Moon eclipse Yelm and it would be a daily affair, happening in the late afternoon.  Spol is, after all, a land of darkness worship within the Lunar Empire, and now you know why...

Sorry, but not at dusk, but rather early in the morning. Spol lies west of the Crater, so you need Yelm rising into the eastern sky rather than sinking in the western sky to have a cast shadow reaching towards Spol.

I think that the moon sits considerably north of the Sunpath, so that any shadow zone would be way far north, probably outside of human-inhabited places.

[Yelm's Light]

Don't look at me.

[kaydet]

Is the eclipse the sign of the kazkurtum?

If so, @Yelm's Light, watch out!

[Minlister]

Fascinating topic!

Isn't there an episode when the bat goddess wraps her wings around Yelm to blind him, enabling his murder? This could be a good eclipse event.

[Byll]

I get lots of eclipses in my 3d model (video here), but they just depend on (terrestrial physics) size, orbital diameter and orbital plane offset and inclination which perhaps should be (Gloranthan physics) importance, and mythological relationship, so that as mentioned while Artia might eclipse Yelm, Shargash might never do so. Moskalf might only eclipse Yelm outside Dara Happa for instance.

Returning to my model, the red moon should eclipse anything on the sunpath or south path. In oder for the red moon to look full in thrice blessed while it is empty in dragon pass it must be relatively low in the sky compared to a circular orbit through the gates of dawn and dusk. If the red moon is high it just always looks about half full as you are looking up at the base of it, all that changes is the (north east south west) direction that the full half is pointing towards.

My assumption is that the planets all have a slightly lower orbit than Yelm and that they never cross the orbit of another planet. I have probably made the planets bigger than they ought to be to make them visible in the resolution of the animation, so the orbits may be further apart than necessary.

I'd forgotten that the sunpath tilts the same way as Polestar, that might be tricky to implement.

Do we know whether the south path is in a plane parallel with the sun path (as in my version) or one that intersects it at the gates? That would make the underworld south path travel north of margastas's pool? (and also make collisions at the gates potentially possible

[jajagappa]

14 minutes ago, Byll said:

Do we know whether the south path is in a plane parallel with the sun path (as in my version) or one that intersects it at the gates?

Neither.

Guide p.647 "This is a highly erratic pathway across the sky. The area from which the Southpath planets rise is called the Eastern Mouth, while the western area where they set is called the Dodging Gate. The meanings of these terms are unclear but widespread, and equivalent names are found in many languages."

Under the subsequent entry for Shargash, it notes "[Shargash] always rises in the exact spot on the eastern horizon, just north of where Lightfore and the Sun rise."

Also under the Artia entry, "the Southpath varies in length"

IIRC, there was a bit more about it in the old Elder Secrets book.  The gist is that it starts in the northeast, north of the Gates of Dawn. The path runs to the southwest (i.e. southward, hence the Southpath), crossing the Sun Path (which allows for celestial battles), and ending at a location in the southwest (well south of the Gates of Dusk) though its position varies (hence "Dodging Gate").

[Minlister]

Oh my Ten Thousands Goddesses!! This is awesome!!!

As an IT-impaired barbarian I kowtow to your skill!!

[David Scott]

This a vast improvement on the old school java version: https://www.glorantha.com/docs/the-movable-ephemeris-and-the-gloranthan-sky/

warning - java's been depreciated in most if not all browsers. Download the zipped version and run it locally.

 

[Joerg]

4 hours ago, Byll said:

I get lots of eclipses in my 3d model (video here), but they just depend on (terrestrial physics) size, orbital diameter and orbital plane offset and inclination which perhaps should be (Gloranthan physics) importance, and mythological relationship, so that as mentioned while Artia might eclipse Yelm, Shargash might never do so. Moskalf might only eclipse Yelm outside Dara Happa for instance.

Don't be so sure about Shargash. According to Jar-eel channeling Sedenya, Tolat was one of the four rebel gods who brought down Yelm, alongside the Bat (Artia?), Sedenya/Verithurusa, and Rebellus Terminus/young Stormy. Tolat is Shargash if the Grazers worship Yelm.

IMO the Southpath never even touches the Sunpath, and the Sunpath never touches the Red Moon even in Summer.

4 hours ago, jajagappa said:

Under the subsequent entry for Shargash, it notes "[Shargash] always rises in the exact spot on the eastern horizon, just north of where Lightfore and the Sun rise."

"north" should be a mistake. Mythically, the only time when Shargash wasn't south of Yelm (in the sky) was when he collided with Umath. He entered the Underworld near the broken North Pillar. It isn't published where he re-emerged. And when he did, neither Yelm nor Lightfor had ever risen in the east.

If the Red Moon is ever eclipsing the Sunpath inside the Lunar empire, then the height of the Red Moon in your model is way too low (or the height difference to the Sunpath is).

 

The planets just pass through Yelm, altering a tiny amount of Yelm's light by adding theirs. It is possible that Yelm's light can pass through or around undiminished, if so such a conjunction could be brighter rather than darker.

I agree that the shadow that orbits the Red Moon would darken the sun. Not sure about the glowing side, though. A total eclipse might still only blot out a minimum of half of Yelm, with the other part could be reddened. But then, the orbiting shadow might be a hemisphere with a much bigger radius than the Red Moon.

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Returning to my model, the red moon should eclipse anything on the sunpath or south path. In oder for the red moon to look full in thrice blessed while it is empty in dragon pass it must be relatively low in the sky compared to a circular orbit through the gates of dawn and dusk.

To avoid that, it would have to hover directly above the Crater.

I tried various geometries for the shadow problem, and basically it is impossible to avoid. Just as you have the Crown Mountains beyond which you cannot look from below, you have a circle roughly the same size below inside which the moon is visible from any direction. This means that neither Full nor Dead Moon can ever be seen anywhere if you assume that lunar glow spreads in straight lines.

On the other hand, we know that the Dead Moon is the absence of Lunar glow, and not the absence of Lunar glow except for that sliver of red on the bottom. Ipso facto some bending of light must happen that prevents transpolar glow  to pierce the shadow, and likewise prevents a dark sliver at the bottom of a full moon. (Transpolar in relation to the bottom pole of the moon...)

 

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If the red moon is high it just always looks about half full as you are looking up at the base of it, all that changes is the (north east south west) direction that the full half is pointing towards.

Assuming that the shadow only creeps over the Lunar surface. It is possible to have an orbiting hemisphere or hemi-ovoid of shadow that blots out the bottom on the dark side and allows a glimpse under the skirt on the bright side. You can play through lots of variations for this orbiter if you assume the top-bottom axis as its rotational axis.

 

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My assumption is that the planets all have a slightly lower orbit than Yelm and that they never cross the orbit of another planet. I have probably made the planets bigger than they ought to be to make them visible in the resolution of the animation, so the orbits may be further apart than necessary.

I'd forgotten that the sunpath tilts the same way as Polestar, that might be tricky to implement.

It might be easier to tilt the ground (and the moon along with that) in your model.

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Do we know whether the south path is in a plane parallel with the sun path (as in my version) or one that intersects it at the gates? That would make the underworld south path travel north of margastas's pool? (and also make collisions at the gates potentially possible

The south path zig-zags across the southern half of the sky dome, never even getting near the zenith (the geometrical construct, not the stellar body that bears the same name). The eastern gate has a more or less fixed azimuth (possibly varying slightly with the tilt of the sky dome), the western gate jumps or oscillates across the lower edge of the sky dome as needed.

Edited July 16, 2019 by Joerg

[Ali the Helering]

If only there were indicators that Gloranthan astronomy was as flawed and religiously motivated as in the RW. 

Oh, hang on a moment..... 

[jajagappa]

2 hours ago, Joerg said:

"north" should be a mistake. Mythically, the only time when Shargash wasn't south of Yelm (in the sky) was when he collided with Umath. He entered the Underworld near the broken North Pillar. It isn't published where he re-emerged.

I don't think so. Mythically/cosmically it makes more sense/fun to have him rise north of the Gates of Dusk and then cross both the Sun Path and Orlanth's Ring at various points. 

[scott-martin]

29 minutes ago, jajagappa said:

Mythically/cosmically it makes more sense/fun to have him rise north of the Gates of Dusk and then cross both the Sun Path and Orlanth's Ring at various points. 

Not taking sides on this but my dumbest comment for the week is to wonder if the north-south axis flips when you enter or leave the hell perspective. In this view, dead "southpath" entities limp mutilated and sad across what to us would be local north of the dead sun path, then their orientation reverses when they clear the Dawn Gate. As a native hell god erupting outside the Gates, Shargash could have experienced that reversal in an abnormal way, showing up in celestial north (still hell south) and then only grudgingly converging with the celestial south path as life in the sky tames his original barbarisms.

For it is written: them what's above / is backward below.

Edited July 16, 2019 by scott-martin

[Sir_Godspeed]

Joerg mentioned this, but I'd just like to add as well: most of the entities in the Gloranthan sky are self-luminous as opposed to RW where they merely are reflective. Therefore they would presumably not "eclipse" the sun in the conventional sense (ie. darken it) even if they passed in front of it.

[g33k]

3 hours ago, Sir_Godspeed said:

... most of the entities in the Gloranthan sky are self-luminous as opposed to RW where they merely are reflective...

hmmm???

The sun is luminous, the moon reflective.  A few sometimes-bright -sometimes-not planets and a few more dim-to-invisible planets...  these appear visually star-like, but are reflective.  And that's it for reflective bodies.

Thousands of luminous stars.

[Byll]

The question seems to be would the luminous but dimmer planets be translucent to the light of the brighter sun, or opaque to it.

Even if opaque, without Netta's cloak covering the sky-dome there would be reflected sunlight reaching the ground being 'eclipsed'. That's part of Yelmalio's manor. 

The planets in my model are luminous but opaque like the sun.

[Sir_Godspeed]

7 hours ago, g33k said:

hmmm???

The sun is luminous, the moon reflective.  A few sometimes-bright -sometimes-not planets and a few more dim-to-invisible planets...  these appear visually star-like, but are reflective.  And that's it for reflective bodies.

Thousands of luminous stars.

We're talking about the planets only here, really, although the difference between planets and stars in Glorantha is less defined than in the RW.

In the RW Mars, a planet, would be a reflective body of mass that could never pass between Earth and Sun.

In Glorantha, Shargash, a planet, is a luminous body of mass that can (hypothetically) pass between Earth and Yelm.

Byll goes on to question whether these luminous bodies are opaque or not, that's a fair question. Even if they are opaque, then what we get isn't the RW "darkening" or even "blackening" of the sun, but more of a dimming.

[Joerg]

6 hours ago, Sir_Godspeed said:

We're talking about the planets only here, really, although the difference between planets and stars in Glorantha is less defined than in the RW.

In the RW Mars, a planet, would be a reflective body of mass that could never pass between Earth and Sun.

In Glorantha, Shargash, a planet, is a luminous body of mass that can (hypothetically) pass between Earth and Yelm.

This depends on how close to clockwork perfection the sky of Time is set up. If you look at the periodic synchronicity of the largge Jovian moons in our solar system, it is quite possible that there are integer relationships between all the movin celestial bodies, with Mastakos/Uleria a third of the period of Yelm and the shortest stable period there is. Yelm and Lightfore together have a stable period, but each of them alone vary quite a bit from that clockwork regularity. If the other planets are as regular as Mastakos/Uleria, it is quite possible that the rise of Tolat/Shargash falls into a well-defined hour, and if that time is outside of the sunrise time span, even a starting point just north of the Gate of Dawn will never create a conjunction between the Red Planet and the Sun. If it falls into that interval, you will probably have two weeks in the year where the conjunction may occur, provided that the Red Planet is in the sky and not in Hell when the tilt of the sunpath would coincide with Tolat crossing. Both Yelm and Tolat are fairly large in area, so that a partial conjunction might be possible in subsequent dawns.

Yelm has at least two conjunctions each day - one (or possibly two) with Theya, one (or possibly two) with Rausa. Both are known to turn his color into a reddish tint.

 

[Sir_Godspeed]

4 hours ago, Joerg said:

This depends on how close to clockwork perfection the sky of Time is set up. If you look at the periodic synchronicity of the largge Jovian moons in our solar system, it is quite possible that there are integer relationships between all the movin celestial bodies, with Mastakos/Uleria a third of the period of Yelm and the shortest stable period there is. Yelm and Lightfore together have a stable period, but each of them alone vary quite a bit from that clockwork regularity. If the other planets are as regular as Mastakos/Uleria, it is quite possible that the rise of Tolat/Shargash falls into a well-defined hour, and if that time is outside of the sunrise time span, even a starting point just north of the Gate of Dawn will never create a conjunction between the Red Planet and the Sun. If it falls into that interval, you will probably have two weeks in the year where the conjunction may occur, provided that the Red Planet is in the sky and not in Hell when the tilt of the sunpath would coincide with Tolat crossing. Both Yelm and Tolat are fairly large in area, so that a partial conjunction might be possible in subsequent dawns.

Yelm has at least two conjunctions each day - one (or possibly two) with Theya, one (or possibly two) with Rausa. Both are known to turn his color into a reddish tint.

 

I was just using the Red Planet as an example by which to show how planets in Glorantha differ from the RW in general. The exact orbital mechanics of Sargash wasn't the focus.