Could it be that simple?

[+ShardlessVessel]

Quote

Questioner 1

You said that moving people like that [Cognitive Shadows] or spren off-world, from Roshar is difficult.

Brandon Sanderson

Yes.

Questioner 1

What about physically, say the Ones Above visit them, and they fly away?

Brandon Sanderson

So one of the things you'll have to be asking questions and theorizing on is what happens if you try to carry a spren around the planet. What happens to their Cognitive sense, right? So you're on Roshar, right? So on the Physical Realm what would happen-- Because on Shadesmar, you have a flattened version. So there are questions for you to be theorizing implicit in that.  And one of them is, what happens, you cross a threshold circling the globe, your spren, what happens to them? Because-- Okay? This relates to the question you’re asking.

Questioner 2

Wait wait, you have a three dimensional plane coexisting with a two dimensional plane?

Brandon Sanderson

Well, two dimensional is the wrong term, but basically...

Questioner 3

Can you specify the mathematically projection used to create this? *laughter*

Brandon Sanderson

We'll try to give it to you eventually, but this is the sort of stuff that I do that Peter's like "Oh man..." *laughter* "Alright give me the math Peter." "Ahhh what do you mean? I'm not a mathematician." "Eh, y'know. You're close." It is very convenient to have a physicist and a mathematician in my writing group.

Arcanum Unbounded Chicago signing (Dec. 6, 2016)

The planet is spherical. Shadesmar is flat. Shadesmar is also compressed, and there are areas where there's a location on the Physical Realm which does not have a corresponding location - or, at least, one of the same size - on the Cognitive Realm.

What if you took a spren, brought it into the Physical Realm (the normal way, by attracting it with emotion or by summoning a Shardblade), and then traveled around the world such that you brought the spren to a spot that does not exist in the Cognitive. What happens?

Could the means for getting a Splinter off their planet be a geography trick? Maybe it's not that simple. I suspect cognitive anomalies may be involved in releasing a Splinter from its planet - the one Cognitive Shadow we know who is also a worldhopper happens to come from a planet with a cognitive anomaly.

[Returned]

1 hour ago, ShardlessVessel said:

The planet is spherical. Shadesmar is flat. Shadesmar is also compressed, and there are areas where there's a location on the Physical Realm which does not have a corresponding location - or, at least, one of the same size - on the Cognitive Realm.

What if you took a spren, brought it into the Physical Realm (the normal way, by attracting it with emotion or by summoning a Shardblade), and then traveled around the world such that you brought the spren to a spot that does not exist in the Cognitive. What happens?

We have a glimpse into this from Rhythm of War via Sja-Anat in Interlude I-2:

 

Quote

She flowed up the steps in one realm, but barely moved in the other. Space was not entirely equal between the realms-- it wasn't that she had a foot in each realkm; more, she was like two entities that shared a mind. In Shadesmar, she floated above the ocean of beads, her essence rippling. In the Physical Realm, she passed among singers who worked in the palace. (RoW, Interludes I-2. I regret that my Kindle copy does not have real page numbers)

So it seems like space is compressed as necessary to maintain a shared physical position for an entity that exists in both realms simultaneously, at least in the realm where physical space is less strictly maintained. That might work equally well in rounding the world, one way or another: you're still just as "in" Roshar in the Cognitive Realm as you would be anywhere else.

Anyways, we don't know if anyone has ever tried anything like that or experimented with something related, so we can't say for certain. I would have to imagine, though, that the Heralds would have had access to this knowledge and the means to make it work if they chose. That none of them have is suggestive.

[Milk]

2 hours ago, ShardlessVessel said:

the one Cognitive Shadow we know who is also a worldhopper happens to come from a planet with a cognitive anomaly.

I don't think this is particularly relevant. Breaths are of Endowment; they can leave Nalthis freely, so I don't think Vasher would face any big trouble. Furthermore, Seons are able to leave Sel, and they are pretty similar to CSs.

[Rg2045]

Could it be that to leave with spren is to simply move though space at super speeds? Maybe the CR has an anchor but the physical realm doesnt?

[+ShardlessVessel]

5 hours ago, Milk said:

Furthermore, Seons are able to leave Sel, and they are pretty similar to CSs.

It's actually supposed to be hard for seons to leave as well (spoilered for length):

Spoiler

Questioner

Do Splinters require proximity to their Shards?

Brandon Sanderson

Do they require it for what?

Questioner

Function--

Brandon Sanderson

Function. It's very hard for most Splinters to leave the realm where they were Splintered, but this gets into tricky stuff because the Shard mostly occupies the Spiritual Realm, but what do you mean by the Shard? Because the essence of the Shard is in the Physical Realm, it's all across the cosmere, and things like this. Usually once something is Splintered it is difficult for them to leave that area, so yes.

Questioner

And in the system--

Brandon Sanderson

You see it with the-- I would call most Cognitive Shadows a Splinter in some ways. And you see it when Kelsier tries to leave, right. And spren would have the same trouble, and seons would have the same trouble. But at the same time is that a proximity to the Shard? Kind of. Things get very wibbly-wobbly timey-wimey when you start dealing with the nature of the Spiritual Realm in the cosmere. 

Oathbringer Leeds signing (Dec. 1, 2017)

Granted, this was before ROW, and probably before he decided to swap Shallan's tamu kek for a seon, and so he may have just changed the rules to make seons capable of leaving without fuss. Or it could mean that the Selish know how to take Splinters offworld - arguably, the Elantrians themselves should have trouble leaving, tied to the Dor as they are, and we know that they managed it centuries ago - and aren't telling anybody.

[Milk]

1 minute ago, ShardlessVessel said:

Granted, this was before ROW, and probably before he decided to swap Shallan's tamu kek for a seon, and so he may have just changed the rules to make seons capable of leaving without fuss.

This same WoB actually suggests that Seons are not bound by the same restrictions as spren. Perhaps it's due to the Shards not actively Investing in the planet? Shades can leave Threnody, according to Secret History.

[Treamayne]

5 hours ago, Milk said:

This same WoB actually suggests that Seons are not bound by the same restrictions as spren. Perhaps it's due to the Shards not actively Investing in the planet?

I think you are reading more into this WoB than is present. BS likes creative misdirection in his answers, he agrees that Sens can go off world, and he agrees that to do so requires the Seon to move into the Cognitive Realm, survive the conditions there and leave the area of Selish Shadesmar. However, he neither states nor implies that those are the only requirements (because that was not the question, so he could be misleading if he wants).

Spoiler

#19 

Paladin Brewer (paraphrased)

Can a spren or seon travel to another Shardworld?

Brandon Sanderson (paraphrased)

Yes they can, though they are more bound to their world, they can travel elsewhere.

Spoiler

#15 

Play/PauseQuestioner 1

When you were talking about spren being bound to the Cognitive Realm of their planet. Are seons similarly bound? Especially with-- Because the--

Brandon Sanderson

Yes.

Questioner 2

Could you also pull them off, with the knowing how?

Brandon Sanderson

Yeah, but you’d have to get through the Cognitive Realm, on Sel. But yeah-- Yes, that is possible.

 

Quote

 Shades can leave Threnody, according to Secret History.

This is not actually the case; in Secret History we see the guards worry that a Threnodite Shade can leave their system and e see that Alonoe disagrees. However, since we never actually see a Shade leave the Threnodite CR, we have no data on which was correct.

Edited June 15, 2022 by Treamayne
Formatting

[Brgst13]

Interesting side note: the WoB you cited in OP suggests that the Spiritual Realm is in fact one-dimensional.  This explains the lack of location concerns and explains why instantaneous transport could happen through the Spiritual Realm.  The interesting part is that the vast majority of Investiture is in the SR, a single point or singularity.  The fact that Investiture can reside outside the SR suggests that something caused this concentration.  Is it possible that the Shattering was a collapse?  The Dawnshards used to pull all Investiture to a single point and caused Adonalsium to rupture due to this concentration?

[Milk]

3 minutes ago, Brgst13 said:

Is it possible that the Shattering was a collapse?  The Dawnshards used to pull all Investiture to a single point and caused Adonalsium to rupture due to this concentration?

I doubt it; spren, highstorms, and other manifestations of Investiture existed pre-Shattering.

[+ShardlessVessel]

14 minutes ago, Brgst13 said:

Interesting side note: the WoB you cited in OP suggests that the Spiritual Realm is in fact one-dimensional.

I disagree about the implication. Brandon immediately denies that Shadesmar is 2D:

Quote

Questioner 2

Wait wait, you have a three dimensional plane coexisting with a two dimensional plane?

Brandon Sanderson

Well, two dimensional is the wrong term, but basically...

And we have seen that it isn't two dimensional. Multiple characters in multiple books have visited the Cognitive Realm and it has all four spatial+temporal dimensions. What Brandon was trying to get across is that the Cognitive Realm does not have the same shape as the Physical. Planets are flattened, for example, but the space itself is not flat.

That said, the Spiritual Realm may be 1D or simply transcend the concept of spatial and temporal dimensions, replacing them for Connection.

[therunner]

5 minutes ago, ShardlessVessel said:

I disagree about the implication. Brandon immediately denies that Shadesmar is 2D:

And we have seen that it isn't two dimensional. Multiple characters in multiple books have visited the Cognitive Realm and it has all four spatial+temporal dimensions. What Brandon was trying to get across is that the Cognitive Realm does not have the same shape as the Physical. Planets are flattened, for example, but the space itself is not flat.

That said, the Spiritual Realm may be 1D or simply transcend the concept of spatial and temporal dimensions, replacing them for Connection.

I'd say that what is meant is that cognitive image of a planet a plane and not a sphere, we saw Kelsier literally walk to the edge of the solar system (or something like it)
The issue there is that those two are not topologically equivalent, so you should have issues for some parts of that image, as they would get stretched or something.

[Brgst13]

1 hour ago, therunner said:

I'd say that what is meant is that cognitive image of a planet a plane and not a sphere, we saw Kelsier literally walk to the edge of the solar system (or something like it)
The issue there is that those two are not topologically equivalent, so you should have issues for some parts of that image, as they would get stretched or something.

This is what I meant by "2-D".  I guess "projection" would be a better term.  I was kind of mixing up terminology.  Physical is a series of spheres separated by space, Cognitive is a series of projections of spheres stitched together, and Spiritual is a point.  Don't know how to describe Spiritual dimensionally, as it's not clear how time works there.  Foresight suggests that time is not the same there but it is not clear if the Realm itself is outside time.

[cometaryorbit]

A single point is zero dimensional, not one: one dimension is a line.

I think the Spiritual Realm just doesn't have physical dimensions at all, they just don't apply: There's a WOB that the Spiritual Realm is not a place.

3 hours ago, Treamayne said:

This is not actually the case; in Secret History we see the guards worry that a Threnodite Shade can leave their system and e see that Alonoe disagrees. However, since we never actually see a Shade leave the Threnodite CR, we have no data on which was correct.

I'm not even sure what's being discussed are Shades in the sense we see in Shadows of Silence - Nazh is from Threnody and says becoming a Cognitive Shadow is an important rite, with requirements and traditions, which certainly doesn't describe the contagious Shades we see (no rites or traditions, just being withered by a Shade makes you one).

Secret History is far enough before Shadows of Silence that this might be Homeland Threnody.

Edited June 15, 2022 by cometaryorbit

[Treamayne]

1 hour ago, cometaryorbit said:

Secret History is far enough before Shadows of Silence that this might be Homeland Threnody.

But, the wounding of Ambition and the disaster on Threnody was before the Splintering of Devotion and Dominion, which was well before Mistborn Era 1 (since that is only ~300 years prior to the Stormlight Archive, and Odium has been trapped in the Rosharan system for at least 4000 years). 

Edited June 15, 2022 by Treamayne
SPAG

[Milk]

5 hours ago, Treamayne said:

But, the wounding of Ambition and the disaster on Threnody was before the Splintering of Devotion and Dominion, which was well before Mistborn Era 1 (since that is only ~300 years prior to the Stormlight Archive, and Odium has been trapped in the Rosharan system for at least 4000 years). 

We don't know whether the Evil occured at the same time as Ambition's death, actually; it might have been unrelated. I think that her Splintering affected the Shades more than the Homeland.

I don't think that we know when Nazh left Threnody, so he may be behind on its traditions or its state.

[cometaryorbit]

5 hours ago, Treamayne said:

But, the wounding of Ambition and the disaster on Threnody was before the Splintering of Devotion and Dominion, which was well before Mistborn Era 1 (since that is only ~300 years prior to the Stormlight Archive, and Odium has been trapped in the Rosharan system for at least 4000 years). 

The wounding of Ambition was very ancient, probably 8000+ years ago, maybe shortly after the Shattering (Desolations on Roshar are 7000 years old - probably Rosharan years so ~7700 Earth years).

But the flight to the Forests of Hell from the Homeland was quite recent, Silence's grandparents were among the first. So quite possibly post Mistborn Era 1.

For some reason the Evil didn't become a civilization destroying threat for a very long time.

Perhaps it was on a different continent than the Homeland and either took a long time to expand that far, or humans finally got ships good enough to reach there and accidentally brought it, or some fragment of it, back to the Homeland?

Or maybe worldhoppers or some other external meddling made it worse?

Or... well, why did Returned only start showing up on Nalthis like 500 years before Warbreaker?