Fun fact: We know the size of the Pokémon world because Scarlet and Violet has framerate issues
Video games tend to do this thing called "culling," where they don't render things that aren't in use. In Breath of the Wild, there's no reason for Link to be able to see how many apples are on a tree in Hateno when he's all the way in Tarrey Town, or know how many Bokoblins are running around Hebra Mountain. Link has a radius around himself that spawns in people, enemies, items, etc, so that the player gets the full experience of a rendered world without the game having to keep track of 850 Hearty Radishes sparkling.
This is good.
Scarlet and Violet has really AGGRESSIVE culling. The devs knew the game was framey and did everything they could up until the last possible second to save on resources.
The player has a single square that's always rendered around them, which takes about 10 seconds to run across. Besides that, all that's visible is whatever the camera is facing; if the camera can't see it, it does not exist.
You might think that this would be good for performance, since the game isn't calling as many assets constantly. And you would be right, if the things culled were ALL that the game was trying to render.
We all know at this point about the memory leak problem the game has, where it won't toss garbage data it's not using. This is supposed to account for the framerate drop; however, if it was ONLY the memory leak, it should start out smoothly, then decay over time until it's unplayable.
So what gives?
This is the ocean.
It's pretty. It's got a tiny bit of reflection, some gentle waves, a nice gradient. A beautifully made ocean without repetitive textures is always nice.
THIS IS THE OCEAN.
IT IS NOT CULLED.
Look at the SIZE of this thing! Paldea is an ANT in the middle of this puddle. It's rendering ALL of this, ALL its sparkles and waves, ALL the time.
Now, this is usually the part of the post where I'm like "and because we know the size of the ocean, based on the coastlines and wind direction, we can figure out how big the rest of the planet is by comparison!" like I did with Breath of the Wild over a year ago.
No.
Another video game term you might not be familiar with is a "skybox." Basically, to give the illusion of faraway objects, clouds, mountains, etc, and to hide the black void most 3D games are built in, games will have a texture wrapped around either the level or where the player is standing. For example:
This is a level from Twilight Princess called Sacred Grove. You normally can't see the bottom parts of this, hence why it turns into a gray plane, but the parts you CAN theoretically see by looking through the trees are colored so you think you're looking at a sky. You can see the edge of the void down in the bottom right corner.
Here's another one from Twilight Princess. You can see the different textures that stack on top of each other, as well as the blue skybox that's centered around Link when he's in the area. You, as the player, FEEL like you're in a small part of a larger world, because the devs cleverly structured together elements you CAN see in other areas into the background.
More complicated versions of skyboxes, typically semi-circular, are called skydomes.
They tend to look kind of like snowglobes, because you do not need to render anything that can't be seen. There's no situation in which the player should be able to fall lower than the level, so there's no reason to render the dome into a sphere in the event that that happens.
In Scarlet and Violet, it would make sense for the skydome to end where the ocean does. There's no situation in which the player manages to go past or underneath the ocean, so even if you wanted a gigantic ocean size like they have, you don't need to use more sky to encompass that.
They did not get this memo.
You might be thinking to yourself "wow, that looks like the curvature of the Earth!"
AND YOU WOULD BE RIGHT!!!!!
Why is this here. Why is it so big. I can't even see Paldea anymore. What exactly was planned for this.
Clever readers might have noticed that I labeled this "Skysphere" and not "Skydome."
That's because it for some reason is a sphere. Paldea is sitting in the middle of a fully rendered gigantic sphere in space. For some reason.
Look at Earth. Look at Spain, which Paldea is supposed to mimic.
I overlaid Spain over Paldea and made them roughly the same size. Assuming the two to be 1:1, the OCEAN is bigger than Earth.
If I then take that size and apply it to the skysphere:
HI. WHY IS THIS A THING.
The skysphere is bigger than the PROPORTION OF THE SUN TO THE EARTH:
I will be taking this as canon sizing until the Pokémon Company comes out and either CULLS this monstrosity and stops forcing our Switches to render THE SUN, or until the Pokémon Company comes out and gives us a canon planet size.