How would the universe change if we grew an extra dimension?

We don’t normally think about it, but the four fundamental force — gravity, electromagnetism, and the two nuclear forces — only have the properties and strengths that they do because they exist in the number of dimensions our Universe has. If we reduced or increased the number of dimensions, we’d change the way that, for example, field lines of force spread out.

This would be catastrophic if electromagnetism or the nuclear forces were affected immediately, as atoms or atomic nuclei could become unbound, change drastically in size, or otherwise create an absolute mess for any bound structure (like humans) that depend on them.

Here’s how that would work. Consider an atom, where electrons orbit a charged nucleus, or the inside of an atom at the atomic nucleus itself. Nuclei and the atoms formed from them are the building blocks of all the matter that makes our world up, and they’re on extremely small scales: Ångströms for atoms (10^-10 meters), femtometers (10^-15 meters) for nuclei. If you allowed those forces to “bleed” into another spatial dimension, which they could do once that dimension reached a large enough size, the force laws governing them would change.