Roshar has tides and sand? How?

[king of nowhere]

I am rereading words of radiance, and i'm noticing little details that seem inconsistent.

In wor chapter 11, shallan just survives the shipwreck, she's on a rock near the shore, and she says that she can reach the coast because of the low tide.

How is there a tide on roshar? The tide is caused by the moon's gravity, and we have noticeable tides on our planet because our moon is pretty big. Roshar has three small moons, but they are said to be roughly the size of phobos. Phobos has such low gravity that a person standing on it could escape the moonlet just by jumping, it could not cause any noticeable tide.

So, how can roshar have tides? is that a mistake?

 

By the way, the same chapter says shallan reached the "sandy shore"; later in the chapter, shallan draws a glyph in the sand. There should absolutely not be sand on roshar, not in an exposed eastern location. This looks like an oversight, except that the sand is referred several times in the chapter. If roshar has no soil because highstorms strip it away, how can it have sandy beaches?

Edited May 29, 2024 by king of nowhere

[Chaos he/him]

I can't comment on sand, but the sun also causes tides on Earth. It's an interaction between both sun and the moon. So there could still be some tides, even if there was no moon.

Or, I don't know, maybe the moons are denser than their size indicates. A moon slept with a queen that one time, so who knows  

[+Lewis Nethur He/Him]

3 hours ago, king of nowhere said:

I am rereading words of radiance, and i'm noticing little details that seem inconsistent.

In wor chapter 11, shallan just survives the shipwreck, she's on a rock near the shore, and she says that she can reach the coast because of the low tide.

How is there a tide on roshar? The tide is caused by the moon's gravity, and we have noticeable tides on our planet because our moon is pretty big. Roshar has three small moons, but they are said to be roughly the size of phobos. Phobos has such low gravity that a person standing on it could escape the moonlet just by jumping, it could not cause any noticeable tide.

So, how can roshar have tides? is that a mistake?

 

By the way, the same chapter says shallan reached the "sandy shore"; later in the chapter, shallan draws a glyph in the sand. There should absolutely not be sand on roshar, not in an exposed eastern location. This looks like an oversight, except that the sand is referred several times in the chapter. If roshar has no soil because highstorms strip it away, how can it have sandy beaches?

Hmmmm...I haven't reread that part in a while but your nitpicking does sound valid...is it reasonably possible that 'high tide' in this context would simply refer to a state in which the sand is fully and completely submerged by water and the tidal forces causing such a state could be derived by the pressure and momentum of each highstorm front? As in: the sand is protected from permanent removal because encroaching storms are the very thing pushing the tide above the level required for storms to sweep them away in a single day?

I'm thinking that rosharans might treat 'tides' similarly to how they treat seasons: transient unpredictable weather states that are driven by distinctly different forces than the earth environment readers would typically intuit independently.

[Treamayne]

5 hours ago, king of nowhere said:

By the way, the same chapter says shallan reached the "sandy shore"; later in the chapter, shallan draws a glyph in the sand. There should absolutely not be sand on roshar, not in an exposed eastern location. This looks like an oversight, except that the sand is referred several times in the chapter. If roshar has no soil because highstorms strip it away, how can it have sandy beaches?

Sand is generally a bio-substance, and usually a product of the marine environment (on which Roshar is based). From the other wiki:

Spoiler

Calcium carbonate is the second most common type of sand, for example, aragonite, which has mostly been created, over the past 500 million years, by various forms of life, like coral and shellfish. For example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years, 

WoBs:

Spoiler

Quote

Ian M Mackay, PhD

Was much of the Shattered Plains inspired by the beach?

Peter Ahlstrom

A lot of the life on Roshar is inspired by tide pools.

General Twitter 2015 (April 10, 2015)

Quote

Peter Ahlstrom

Roshar's moons are much much closer than our moon. Their elliptical orbits bring them closer to Roshar's surface during the night than geosynchronous altitude.

Robot Aztec

Are the tides funky for moons then? Or are moons too small?

Peter Ahlstrom

They are very small. Think Phobos and you'll be in the ballpark.

Miscellaneous 2014 (Feb. 27, 2014)

 

Sandy beaches, in a storm surge, will often wash off shore into sandbars (which Shallan also mentions, because the Santhid leaves her on one) but they do not tend to "blow away" due to surface wetting forces. The mass of individual grains is much smaller than the mass of the water droplets holding them down and together - which is wny you get sand storms in desert environments, but not beach environments. 

As for the tides - sure each moon is smaller than our moon, but you have tidal gravitation from (at least) four distinct sources (their sun and three moons, which each pass much closer to the planet than ours). I imagine the tides on Roshar to be very complex, but with a lower average tidal differentiation than we would see in our world (NOAA links - Nova Scotia can be as great as 38+ feet). I would also expect that, like @hwiles said, part of the effect they are seeing is storm surge from the Highstorms while off-shore, which they simply call "tide" because of the similar effect of offshore storms interacting in the beach environment. 

Hope that helps

[alder24]

5 hours ago, king of nowhere said:

So, how can roshar have tides? is that a mistake?

Sun's tidal forces are half as strong as those made by the Moon. 

[king of nowhere]

18 hours ago, Treamayne said:

Sand is generally a bio-substance, and usually a product of the marine environment (on which Roshar is based). From the other wiki:

  Hide contents

Calcium carbonate is the second most common type of sand, for example, aragonite, which has mostly been created, over the past 500 million years, by various forms of life, like coral and shellfish. For example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years, 

WoBs:

  Hide contents

 

Sandy beaches, in a storm surge, will often wash off shore into sandbars (which Shallan also mentions, because the Santhid leaves her on one) but they do not tend to "blow away" due to surface wetting forces. The mass of individual grains is much smaller than the mass of the water droplets holding them down and together - which is wny you get sand storms in desert environments, but not beach environments. 

As for the tides - sure each moon is smaller than our moon, but you have tidal gravitation from (at least) four distinct sources (their sun and three moons, which each pass much closer to the planet than ours). I imagine the tides on Roshar to be very complex, but with a lower average tidal differentiation than we would see in our world (NOAA links - Nova Scotia can be as great as 38+ feet). I would also expect that, like @hwiles said, part of the effect they are seeing is storm surge from the Highstorms while off-shore, which they simply call "tide" because of the similar effect of offshore storms interacting in the beach environment. 

Hope that helps

Makes enough sense for sand - though if soil, which is held together by similar mechanisms, is eroded away, then a beach should too.

Does not make sense e for tides. Doesn't matter how close the moons are, they are too small to cause a tide. They would not cause a tide if they were on the surface. The highstorm explanation doesn't hold, because there was no highstorm for the whole next day. 

The sun explanation is the only one with some merit regarding tides

[JohnnyKaizen he/him]

On 5/29/2024 at 7:42 AM, Treamayne said:

As for the tides - sure each moon is smaller than our moon, but you have tidal gravitation from (at least) four distinct sources (their sun and three moons, which each pass much closer to the planet than ours). I imagine the tides on Roshar to be very complex, but with a lower average tidal differentiation than we would see in our world (NOAA links - Nova Scotia can be as great as 38+ feet). I would also expect that, like @hwiles said, part of the effect they are seeing is storm surge from the Highstorms while off-shore, which they simply call "tide" because of the similar effect of offshore storms interacting in the beach environment. 

Hope that helps

I'd also like to point out that based on stories told throughout the SA, I assume that the moons are (to some degree) invested, and may contribute to the tides more than their size would otherwise indicate. Braize and Ashyn are also nearby (relatively) and almost certainly invested (Odium is linked to Braize, and while Odium specifically tried to not invest himself in Ashyn, there is magic there, probably from Adonalsium but wherever it's from, It's invested) and could also have an effect on the tides. Is there another system in the Cosmere (that we know of) with multiple planets that all have direct connections to Investiture, because I'm drawing a blank atm? Either way, I feel like the question isn't "why does Roshar have tides," but more like "Why doesn't Roshar have tidal waves?" 

[+Lewis Nethur He/Him]

10 hours ago, king of nowhere said:

...

The sun explanation is the only one with some merit regarding tides

Yeah, I can't explain the sand part; I assume Sanderson must have just felt it was more thematically appropriate than a beach of bedrock and clay for a scene following a shipwreck. Those types of anomalies are difficult to identify, so good on you if no one comes up with a rock solid explanation.

I think @alder24 nailed it with the sun being the main source of the tides though. Thinking on it more, Roshar is smaller and spins faster than the Earth, so...if their sun happens to be a little larger or denser than the Earth's, then they could plausibly have tides similar to ours.

[JohnnyKaizen he/him]

58 minutes ago, hwiles said:

Yeah, I can't explain the sand part; I assume Sanderson must have just felt it was more thematically appropriate than a beach of bedrock and clay for a scene following a shipwreck. Those types of anomalies are difficult to identify, so good on you if no one comes up with a rock solid explanation.

I think @alder24 nailed it with the sun being the main source of the tides though. Thinking on it more, Roshar is smaller and spins faster than the Earth, so...if their sun happens to be a little larger or denser than the Earth's, then they could plausibly have tides similar to ours.

We don't know a lot about the ecosystems of the oceans on Roshar. We do know there is marine life. If there's as much or more coral as there is on earth, why would the presence of sand be surprising? All it takes is for something akin to parrot fish to produce sand. It would shift around from the highstorms, but it would still collect over the millennia on and near the coasts. Also, the highstorms don't act like hurricanes. They're straight line winds that blow from east to west. It's logical to assume that the ocean level raises ahead each high storm as the force of it pushes across the ocean, before it makes landfall. While those waters would retreat and drag sand with it, it wouldn't drag the whole beach away, nor would beaches really be exposed to the winds as the water would be covering it before the highstorm winds arrive.