Arbitrary positions in space are 'the void', and we can think in terms of going from one point to another: this consists of vectors. We can try to figure out angles between: this requires a familiarity with trigonometry.
The void requires a lot of mathematical knowledge and skill to conquer. Practical examples may help with visualisation: one corner of a cardboard box to another - how to measure that distance - compared to working it out using mathematics.
If boxes are not hard enough, what about more complex 3D shapes: cones, spheres, polyhedra...
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