[Karellen]

> KK theories introduce an extra spatial dimension beyond our usual (3+1) which is postulated to be "compactified". This just means that it's curled up on itself

You've just explained "compactified" in terms of being "curled up", but that doesn't really help (for me, at least). What does it mean for a dimension to be "curled up"?

[elashri]

I'm sorry if I'm confusing. That's the term I use, usually assuming that it is obvious (like referring to C++ templates to a python developer without explaining what is that).

To be honest, it is hard to visualize, as it is counterintuitive of what we think of space. While I know many people would disagree, I really like the garden hose analogy [1]. The idea is to simply imagine a very long garden hose. From a great distance, it looks like a one-dimensional line. Now you get closer, and realize it has a second dimension, which is its circumference curled around that seemingly 1-D line. An ant walking on the hose can move along its length, but also in a circle around it. The extra dimension in KK is like this circumference. It is tiny, curled up so we don't directly notice it, but still potentially there.

[1] https://www.preposterousuniverse.com/blog/2004/06/30/extra-d...

[Izkata]

This kind of makes me think of a spatial version of the Time Cube.