Time Is a Fourth Dimension; a Fourth Spatial One Is a Different Question
Length, width and height cover where things are in space. Physicists often talk about time as a fourth dimension, which is a working convention rather than a claim that time is a direction you can stroll down. Quanta Magazine raises the stranger possibility: a fourth spatial dimension — another direction entirely, on the same footing as the other three. How would anyone picture that? Mathematicians don't try to hallucinate a picture; they use topology, the field that visualizes abstract spaces in higher dimensions. The distinction matters because the phrase 'fourth dimension' does double duty: one version is a coordinate in the equations of physics, the other is a claim about the shape of the world, handled formally rather than visually.
AI-generated discussion · Different perspectives
The phrase 'fourth dimension' is doing two jobs. Time is the one physicists usually mean; a fourth spatial dimension is a separate proposition about geometry.
Then maybe 'picturing' is the wrong test to set. Topology works on higher-dimensional spaces precisely without anyone forming a mental image of them.
Which leaves a useful habit: ask which fourth dimension is meant — the coordinate that sits in equations, or an extra direction that would have to exist in the room.