The Moons of Roshar

[Oudeis he/him]

Are they always full? I can't remember if it's ever mentioned them being waxing, waning, or new.

[StoneWalker he/him]

The orbits of the moons suggest that yes, they are always full, at least when they come out at night.This actually makes more sense than we might think, since the moons are closer than ours and rotates so that they orbit at least once per day, instead of once every 28 days. This allows for the moons to always be on the opposite side of Roshar from the sun and appear full at night.

It's possible, but I'm now speculating wildly, that the moons do appear new, by passing twice each day, once during the day and once again at night. Otherwise the other side of Roshar always gets new moons in the day and not at all at night. Both are possible, but I'm not sure if there would be a way to tell the difference.

Edit for clarity and grammar.

Edited August 18, 2015 by StoneWalker

[Ansalem]

The orbits of the moons suggest that yes, they are always full, at least when they come out at night.This actually makes more sense than we might think, since the moons are closer than ours and rotates so that they orbit at least once per day, instead of once every 28 days. This allows for the moons to always be on the opposite side of Roshar from the sun and appear full at night.

It's possible, but I'm now speculating wildly, that the moons do appear new, by passing twice each day, once during the day and once again at night. Otherwise the other side of Roshar always gets new moons in the day and not at all at night. Both are possible, but I'm not sure if there would be a way to tell the difference.

Edit for clarity and grammar.

 

I'm having a hard time figuring out the moons. They move across the sky at the same time each night in the same pattern each night. We know this because of so many different references to using the position of the moons to judge the time. You wouldn't be able to do that just by looking unless the pattern never changed. You could if you memorized the lunar cycles for every single day, but nobody ever references any charts about it, so we can assume they just know by looking up. The problem with that is in order for them to always be at the same point at the same time every day they need to be in geostationary orbits which means they would always be in exactly the same spot and not move across the sky. Granted I'm not very good with imagining 3-dimensional motion like that, but I can't imagine any other speed working, it would have to be geostationary, otherwise you would get phase cycles.

 

So the only 2 explanations I can think of are either: 1) they're always in the same position relative to the planet and the sun as you said, or 2) they speed up on one side and slow down on the other side somehow. Neither one of those makes any sense to me, honestly.

 

If they're always opposite the sun relative to the planet then they're orbiting very slowly, slowly enough that they should just crash into the planet instead of orbiting. On top of that, if the planet is rotating along the same direction as its orbit (which is very likely) then the moons are orbiting in the opposite direction of the planet's rotation. That would cause gravitational dragging on the planet which would be slowing the rotation of the planet down which would cause all sorts of problems, not least of which it would throw off the pattern over time. If that's what's happening then eventually Roshar is going to end up tidally locked with its star, at least for a time, which basically means all life will be destroyed. The True Desolation doesn't even need to happen in that case, a tidally locked planet will eradicate all life all on its own. The True Desolation will seem like a minor nuisance by comparison.

 

If the moons are on an orbit where they speed up and slow down on different sides of the planet then in order for them to always be visible at night it means that the faster orbit is on the night side of the planet. That means that the orbit moves farther away from the planet on the day side, in other words they move toward the sun. If that's the case they should just fly into the sun instead of coming back around at regular intervals. They would probably keep orbiting for a while but the planet shouldn't have any moons at all by now, unless the planet and/or moons are very new. They shouldn't have ever gotten onto that orbital path in the first place, though.

 

Actually, I lied, I can think of 3 explanations but I wanted to explain away the others first since the third is what you suggested. So they aren't in geostationary orbit, they aren't in the same position relative to the sun, and they aren't changing speeds.  The only possibility, seems to me, is that the moons are orbiting at exactly twice the speed the planet rotates. It has to be exactly twice the speed, though, otherwise the pattern would be off and you couldn't tell the time just by looking at their positions. You would get phase cycles. The likelihood of that happening with 3 moons is astronomical. Hell, the likelihood of it happening with just one moon is astronomical. 

 

I'm going to say that the moons were put in that orbit intentionally by one or more of the Shards, or maybe Adonalsium itself. It's possible, I think, just based on physics but insanely unlikely.

 

Dunno why I felt like typing all that out after you already provided the obvious answer, I just never thought about Roshar's moons, they were just kinda there to me, and I love this sort of stuff.   Mostly I wanted to point out why your wild speculation is the only possible answer and not wild at all. Although I could be missing something. Maybe one or more of the shards are just acting against gravity for whatever reason to keep them in an illogical orbit. Who knows.

 

edit: I just realized, they might be orbiting the planet perpendicular to the planet's orbit. North and south instead of east and west. Would that work? I think it could. Actually yeah if they're full for the entire night then that has to be the case otherwise you would see all of the phases every night. They still have to be orbiting at either the same speed as the planet rotates or at twice the speed. I don't know if it's ever specifically mentioned whether they go through phases at night or how fast they move across the sky, though. What an incredibly strange orbit that would be. It would have to be a spiral orbit to avoid phases I think. My brain is breaking.

Edited August 18, 2015 by Ansalem

[DreamEternal]

If their orbit is that unstable, maybe Odium plans to drop them on the planet after killing Cultivation.

EDIT: Actualy, after weakening her just a little, since if he was the only shard left he could easily drop Roshar into the Sun or launch it towards Scadrial at a significant fraction of the speed of light while he goes hunt other shards.

Edited August 18, 2015 by CognitivePulsePattern

[Kurkistan he/him]

There are several WoPs on this thread that might be of interest; the specific post linked to has Peter saying that the moons were put in their orbits artificially.

[Ansalem]

There are several WoPs on this thread that might be of interest; the specific post linked to has Peter saying that the moons were put in their orbits artificially.

 

 

I think they almost have to be put there artificially. He does say that the orbit is unstable which tells me that it could actually be that they are orbiting slowly and backwards. But if that's the case then Odium could simply wait for the inevitable destruction of Roshar. It also means that either the planet, the moons, or both are very new in astronomical terms. It could also be one of the other two possibilities I suggested. They could be orbiting at twice the speed the planet rotates, that could definitely be unstable because it means they're probably very close to the planet which is bad for gravity reasons. Could also be the spiral north-to-south orbit I mentioned, which would be awesome, but it's just a variation on the double-speed orbit. They would still have to be very close and the spiral itself would have to be unstable, the planet must have a crazy axial tilt wobble.

 

None of the possibilities are very good in the long term. If Odium were a patient Shard he could just wait and not bother with Desolations, though I suspect his nature compels him to act. He is effectively immortal though so astronomical time scales shouldn't matter. Roshar is going to be destroyed by those moons in one way or another in the million to billion year range. I'm about 75% confident in that, knowing that the orbit is definitely unstable. Though if they were artificially placed they might also be artificially maintained.

 

Who knows. I'm content to just say that they're really freakishly weird.

[StoneWalker he/him]

edit: I just realized, they might be orbiting the planet perpendicular to the planet's orbit. North and south instead of east and west. Would that work? I think it could. Actually yeah if they're full for the entire night then that has to be the case otherwise you would see all of the phases every night. They still have to be orbiting at either the same speed as the planet rotates or at twice the speed. I don't know if it's ever specifically mentioned whether they go through phases at night or how fast they move across the sky, though. What an incredibly strange orbit that would be. It would have to be a spiral orbit to avoid phases I think. My brain is breaking.

 

I also thought that it could be perpendicular, but I realized that they could be in almost any orbit different from the orbital plane of Roshar. That way they never transit in front of the Sun, which would almost certaintly be noticed, since it would probably happen three times a day. If they are as small as I remember hearing, something like one is about the size of Ceres and or Rhea then they would probably never be able to actually create a full eclipse. That said, you probably could see a first quarter moon right at the second moon rise, which would quickly wax to full, and possibly some other phases if you were really paying attention. Their size would also make it hard for you to tell the difference between a gibbous moon and a full moon.

 

Nice to see that my "wild speculation" was actually pretty much what your conclusion was.

[DreamEternal]

I think they almost have to be put there artificially. He does say that the orbit is unstable which tells me that it could actually be that they are orbiting slowly and backwards. But if that's the case then Odium could simply wait for the inevitable destruction of Roshar. It also means that either the planet, the moons, or both are very new in astronomical terms. It could also be one of the other two possibilities I suggested. They could be orbiting at twice the speed the planet rotates, that could definitely be unstable because it means they're probably very close to the planet which is bad for gravity reasons. Could also be the spiral north-to-south orbit I mentioned, which would be awesome, but it's just a variation on the double-speed orbit. They would still have to be very close and the spiral itself would have to be unstable, the planet must have a crazy axial tilt wobble.

None of the possibilities are very good in the long term. If Odium were a patient Shard he could just wait and not bother with Desolations, though I suspect his nature compels him to act. He is effectively immortal though so astronomical time scales shouldn't matter. Roshar is going to be destroyed by those moons in one way or another in the million to billion year range. I'm about 75% confident in that, knowing that the orbit is definitely unstable. Though if they were artificially placed they might also be artificially maintained

Remember that if there is something Roshar does not lack, it is investiture that predates the shards. As far as we know, there may be a giant godspren in each moon that keeps it from falling, wich would also explain why Odium can't just push them slightly into a fast downward spiral of certain doom.

[Ansalem]

 

I also thought that it could be perpendicular, but I realized that they could be in almost any orbit different from the orbital plane of Roshar. That way they never transit in front of the Sun, which would almost certaintly be noticed, since it would probably happen three times a day. If they are as small as I remember hearing, something like one is about the size of Ceres and or Rhea then they would probably never be able to actually create a full eclipse. That said, you probably could see a first quarter moon right at the second moon rise, which would quickly wax to full, and possibly some other phases if you were really paying attention. Their size would also make it hard for you to tell the difference between a gibbous moon and a full moon.

 

Nice to see that my "wild speculation" was actually pretty much what your conclusion was.

 

 

That's a good point. I do think they're pretty small, though I can't remember why I think that. When I said "perpendicular" I was really imagining a sort of diagonal spiral because if it were truly perpendicular the moons would always be dark, I think, or mostly eclipsed at least and they wouldn't rise above the horizon. A spiral in the sense that it moves along the same path across the planet but rotates as the planet orbits the star, in order to always be lit the same way and in the same positions in the sky year-round. But you're right I don't think that's necessary now. I don't know where in the sky they move, are they ever directly overhead? Either way I think you're right, they could be in almost any orbit other than parallel or directly perpendicular. If they don't spiral like that, though, they should be in different places in the sky throughout the year. But they could still be relatively regular enough to tell time by I think.

 

edit: Well, actually they could be perfectly perpendicular, it depends on where the continent is located on the planet what that would look like.

 

For a second there I started to wonder if maybe Roshar is rolling along its orbit like Uranus does but then I reminded myself to not be a crazy person.

 

 

Remember that if there is something Roshar does not lack, it is investiture that predates the shards. As far as we know, there may be a giant godspren in each moon that keeps it from falling, wich would also explain why Odium can't just push them slightly into a fast downward spiral of certain doom.

 

 

Yeah that's basically what I was thinking about. Or it could be something Cultivation is doing or Honor did. Maybe even Odium for unknown reasons. It's said that each moon is related to each Shard but that could easily just be mythology or coincidence.

Edited August 18, 2015 by Ansalem

[natc]

I recall the continent just being one big thing in the southern hemisphere and everything else is water. But not sure.

[Juanaton he/him]

They could be sitting in the LaGrange points while the planet turns beneath them...just saying they don't have to "orbit" at all to always appear full and provide a timekeeping device...at least, I think that could work.

[ccstat he/him]

That is a good thought, but since all three moons transit serially in the course of the night, they must be much closer at the time of transit than the LaGrange points. I like the idea, though! Way to consider other angles.

[ParadoxicalZen he/him]

 

 

LEIYAN

Can you tell me which is the most massive moon [of Roshar]? Not the biggest, but the most massive.

BRANDON SANDERSON

I think the biggest is the most massive. All three moons are much closer than our moon is.

LEIYAN

And so is that Nomon?

BRANDON SANDERSON

Yes.

LEIYAN

How big is Nomon on the night sky, like compared to our moon?

BRANDON SANDERSON

Larger than our moon, but not dominating of the sky. [...] I do believe Nomon is bigger, but I had to have Peter run those calculations, so he may come back and say no Brandon, that's not possible, but I do believe it's bigger than our moon in the sky. You're supposed to be able to see moderately well by Nomon.

LEIYANSo I had some things I figured out, I just wanted to know if they're true or not. So I have that the orbits of the moons would precess so that the farthest point is always pointing towards the sun.

 

BRANDON SANDERSON

So, one more time.

LEIYAN[uses diagram to explain the question]

 

BRANDON SANDERSON

So, we have figured all this out. It's in the wiki--so me just saying--it's not in the wiki that you can find. I would need to go compare this. All the calculations on things like this--this is stuff where I sat down with Peter, who knows much more astronomy than me and said "here's what I want" and he's like "well it has to be this" and I put that in.

LEIYANDo you know, do the moons orbit the opposite direction to Roshar's rotation?

 

BRANDON SANDERSON

I believe they do but I'm not 100% sure.

LEIYANThere's no eclipses as far as I can tell, so the plane of the orbit must be strongly inclined, 'cause there'd be an eclipse every day if there were eclipses-

 

BRANDON SANDERSON

We had to fudge that because as you said, if there were any it'd be all the time.

http://www.theoryland.com/intvsresults.php?kwt=%27roshar%27

WoB from TL and cut for relevance, WoB number 36

 

Doesn't answer all of them 

[Oudeis he/him]

My reason for asking: I suddenly got to thinking how whenever I thought of them, I thought of them as full. I know it's referenced pretty frequently that they provide a lot of light, and it got me to wonder if they're always full (or perhaps just never entirely dark?)

 

But then I got to thinking. If they are always full (or possibly even if they're not), do we know they operate like normal moons? Is it possible they glow with something other than reflected glory? Stormlight? An entire other kind of light? Spacelight? Voidlight? Are they reflecting something other than sunlight?

 

Also just gonna toss this out there. I think they aren't actual moons. They seem to travel very quickly across the visible sky, then cross the far side of the planet at a greatly reduced rate. What if they're piloted vessels somehow? What if someone or something send them rapidly across the night sky in order, then holds them each on the far side of the planet during the day, like the tale of Helios and his chariot, or Ra with his barge? It would be very Sanderson to take a common theme of mythology and say, but what if that were actually the case, ironically on a world that has no similar myth?