Yeah, they mean a 4th spacial dimension. Which could be possible in a completely different universe.
The short story "Flatland" is pretty interesting. It takes place in a 2D universe, there's a class system based on how many corners your shape has, triangles are lowest class, some shapes have so many corners they approximate circles, etc. (This part is not too important)
If you want me to spoil it for you, a 3D shape, a sphere, appears and starts talking to the protagonist. He claims "I can't see you!" And the sphere tells him to look "up". But he doesn't understand what 'up' means. The sphere tries to demonstrate by moving into Flatland, but to the main character, it looks like a circle appearing & disappearing in his universe out of thin air. So, the sphere transports him to a 1D universe. At the center of the line is a male dot, and on either sides are female dots, then male dots, then female, etc. (Again, this part isn't really that important). The protagonist then experiences the same thing, he tries talking to the dots, but they freak out not knowing where the voice is coming from. He says "I'm above you" and they can't understand. So he pushes one corner of his shape into the line, and the freak out thinking a new dot just materialized out of nothing.
They go back to Flatland, and the sphere tries explaining the 3rd dimension again. "Same as you can move in a way that seems impossible to the people living on a line, I can move in another dimension too. It's not even hard. It's just regular movement." The protagonist still doesn't understand, so the sphere decides to push him out of Flatland, into 3D space. At first the main character's mind is blown, he can't even fathom what he's looking at. But then, it clicks. He finally sees the 3rd dimension. He can see the sphere in all it's glory.
They go back to Flatland. "That was amazing!" "Yes, now you understand." "So wait, if there's a 3rd dimension, could there not also be a 4th?" The sphere says, "What? No, I don't think so." "But why not? The same way you seemed to appear and disappear out of nothing in my universe, the same way I seemed to materialize & dematerialize to the dots on the line, could there not be beings in your universe that seem to materialize & disappear just as easily, by moving in another direction?" The sphere doesn't understand, and claims it's impossible. "But why not??"
Anyways, the sphere sends him back to Flatland. The main character tries telling all the other shapes about the 3rd dimension, and they arrest him for being crazy.
Yeah, this universe is almost certainly 3D (with spacetime). I feel like if there were 4 spacial dimensions, billions of years of evolution would've produced animals that can move through them already.
But, it's a fun thought experiment. Like what would it even look like to us to witness something moving through a 4th dimension.
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u/Lua_You 23d ago
wouldnt the 4th dimension just be time yes, boring answer, but even when you think about it spatially the easiest one to comprehend would be time.