Today, I'm gonna do a multimedia post (by which I mean a blog with a few diagrams). Essentially, I'll be addressing the common trope of "traveling to another dimension", and whether there's any scientific accuracy to this.
So, first, let's define a "dimension". We live in a 4 dimensional universe. There are three spacial dimensions, which we can think of as up/down, left/right and forwards/backwards, and one temporal dimension (in other words, time exists). A dimension does not refer to, say, a parallel universe. So does that mean the trope is completely inaccurate? Well... No. If we want to consider it, though, we need to consider a 4th spacial dimension.
Let's take a step back though. We should look at lower dimensions first. First, let's look at a cube. If you take an infinitely thin slice of the cube (along a certain axis), you'll get a square. If you take an infinitely thin slice of the square, you get a line. If you take an infinitely thin slice of the line, you get a dot. So if we extrapolate, then we can say that taking a slice of a 4 dimensional shape can give us a 3 dimensional one, such as a cube. This is probably hard to imagine, but you have to take into account that the shape extends into a dimension that human minds physically can't comprehend. So that's fun.
Now, let's imagine a 2D world...
...That wasn't too hard. What you have to realise though, is that we're looking at this world 3 dimensionally. The characters in it can comprehend left/right and up/down (in the same way a computer screen can, coincidentally), but not into and out of the screen. So what would happen if we could somehow push a 3D object into the screen so it intersected the 2D world?
In case it isn't clear- that's a cube, oriented with one corner facing out of the screen. The bit that intersects the 2D plane is shaded in grey, and in this orientation, it makes the shape of a triangle. To the people in the universe, there is now a triangle there, but to us, there is a cube intersecting their plane of existence. If you can imagine moving the cube, it would appear to them as the triangle changing size, and eventually, shape.
There's another important thing to mention here. Since the world we're imagining is 2D, it takes up zero space along the in/out of the screen dimension, which means we could place an infinite number of these worlds side-by-side in a room, as long as they're parallel. It also means that it's impossible to make any force in that direction- the characters could move objects up and down, and side to side, but never into or out of the screen. Not only would these worlds not be able to observe one another, but they couldn't interact.
However, if a 3D object were to pass through one of these worlds (as in the diagram), it could in theory push objects along that 3rd dimension, meaning they could move from one 2D world to another.
So what does this all mean? Well, if we assume that everything here is true (which in theory it should be, though I don't know how well this would apply to reality), then we could extrapolate these ideas to work in 3D space. A 4D object traveling along a 4th dimension could theoretically push things out of existence, and into another existence. It also explains why 4D objects are always illustrated as constantly moving- what they're really showing is an animation of what the object would look like as it passed through our world, not unlike the morphing triangle that would appear in 2D space with a cube.
So, back to the original question at hand- is traveling to other dimensions possible? No. But traveling along other dimensions might be (assuming a 4D object was available to push you). It also means the terms "plane of existence" and "parallel universes" might just be more accurate than most people realise...
I'm sorry, but yes. This whole post was just a lead-up to that bad punchline.
Yeah, okay. But the point still stands- the idea of traveling to other dimensions is somewhat flawed, but theoretically, traveling along other dimensions could take you to other universes.
It's also worth noting- the idea about showing a cube intersecting a 2D plane isn't mine. It was in an animation on YouTube by a channel called "Miegakure", which honestly does a better job showing it than I ever could. If you find it interesting, check the channel out.
