So I have been wondering. How big is the spiral and where is the Arcanum and earth located?
It was stated by Bartleby that the spiral is a thread that holds the Universe together. So the spiral should be at least the size of a universe, on contrary to a developer presumably saying it's a Solar System. We know the earth exists outside the spiral. Therefore it has to be outside of the universe of the spiral, otherwise Bartleby's statement at the start of the game is wrong. Which would create so many inconsistencies in the game. Furthermore, the Arcanum exists where? Outside the spiral? That would mean it exists outside the universe.
So I would recommend you don't make a mountain out of a mole hill.
What is a universe?
Our universe is generally thought to be rather large- however, just because ours is large doesn't mean that all universes must need be large. I think it is totally fine for the Spiral Universe to be "galaxy" or "solar system" sized.
You must also consider that a Universe is really perhaps more related to a "reality" in this sense. Bartleby makes no claim to hold the multiverse together.
I expect that the Arcanum exists both within and without the Spiral and is probably phasing between the Spiral and another pocket universe/reality.
Basically, I don't think your logic holds. Again though, all of this depends on your definition of terms and your perspective. And does your perspective and that of Bartleby match?
I would argue that the Spiral is more like a galaxy than either an entire universe or a small solar system. Our own galaxy is a spiral shape!
If the Arcanum is "in space" outside of the Spiral, then it would be similar in concept to an intergalactic ship that can travel between galaxies.
You're right, though. If the spiral is only a galaxy and not the whole universe, then Bartleby misspoke. Then again, he's missing his Eye of History (Malestaire stole it), so perhaps his memory of how the spiral formed is not complete. He's like a very ancient old guy who recalls the most important part but sometimes gets the details wrong.
The universe by definition is "all existing matter and space considered as a whole; the cosmos [...] and contains a vast number of galaxies". It's never meant to be anything else.
Medulla even said Spider would destroy "THIS universe", obviously referring to the spiral, as his plan has nothing to do with things outside of it. He himself just wants to rewind the spiral back to the Firstworld/destroy the spiral.
Earth is even supposed to be completely outside the spiral. I think the lore of the game is great, but they REALLY need to explain a lot of stuff. Such as the size of the spiral, if earth is in another universe etc.
So I have been wondering. How big is the spiral and where is the Arcanum and earth located?
It was stated by Bartleby that the spiral is a thread that holds the Universe together. So the spiral should be at least the size of a universe, on contrary to a developer presumably saying it's a Solar System. We know the earth exists outside the spiral. Therefore it has to be outside of the universe of the spiral, otherwise Bartleby's statement at the start of the game is wrong. Which would create so many inconsistencies in the game. Furthermore, the Arcanum exists where? Outside the spiral? That would mean it exists outside the universe.
I have a jumper (sweater) that has a broken thread. The thread is neither the entirety of the jumper, nor as big as the jumper, but when it broke the whole jumper began to unravel.
If the Spiral is a thread that holds the universe together, if it is damaged or broken the Universe far beyond the reach of the thread itself could be affected and start to unravel. I don't think Bartleby misspoke and there may be many equally significant threads holding the Universe together.
Coming from a Comic Book Geek background, I interpret Bartleby's statement of "universe" to be better defined as "the known reality", not THE Universe. Comic books have long postulated different quantum realities where minor differences define the "universe".
A very good read on the nature of parallel universes is Robert Heinlein's "Number of the Beast"
My take on the "reality" of W101 is this; way back when it was "One World" before the sundering that produces the worldlets, that one world was very Earthlike with multiple ecosystems, languages and cultures. This world however was populated by anthropomorphic animals as well as humans. Magic is/was more accessible in the W101 reality than in our own. When this world was torn asunder it became a solar system sized archipelago of worldlets pulled from the various eceosystems, cultures, and timeline of the original world.
Bartleby, Grandmother Raven, and Grandfather Spider put the spiral doors in place to keep the worldlets connected. Over time the various races learned to navigate the space between worlds (witness the ships of Grizzlehiem and P101 or the air ships from Marleybone the crash landed in Celestia).
All this to say that when Bartleby says Universe, he means "The Spiral" which judging from the maps in Ambrose's Study and the center of the Arcanum is solar system sized and the complete sum total of all existence.
Also, it's a game. Sometimes we don't need to dig to deeply into the world building of the game.
If you have completed the Briskbreeze Tower, a reference is made to "something coming to the Spiral". This insinuates that the Spiral is located within something larger (i.e. some kind of Universe). Since there are numerous references that the player is from Earth, I would assume that larger something is our Universe.
The problem also is, there are supposedly "countless" amounts of worlds across the spiral, stated numerous times. And these worlds are significantly afar from each other. If it was just the size of the solar system, there wouldn't be "countless" worlds [Each seem to be the size of an island or bigger]. At the smallest, the spiral has to be a galaxy/
Furthermore, the shadow web is a universe, as stated by Morganthe. And in the prophecy in Khrysalis, the shadow web would touch the entirety of the spiral, not beyond that. There's still Medulla saying "THIS" universe (referring to the spiral as Spider's plan has NOTHING to do with anything outside of it) would be destroyed, implying there is in fact a multiverse, and the spiral is potentially just 1 universe in said multiverse.
The most confusing thing is the Firstworld though. We don't know how big it actually was. We just know it's big enough to make countless fragments.