Starting Work on an Extra Dimensions Section

I’ve done some work today on writing the first parts of a section on Extra Dimensions of Space, a very important but very large topic.  It will probably be months before the whole thing is fleshed out, but some of you may be curious to read along as it takes shape.  In particular, you can’t understand extra dimensions of space if you don’t understand dimensions properly, so I’m starting from the point of view that I need to explain how I and many other physicists think about dimensions in general, and spatial dimensions in particular. Right now, of several planned sub-articles, only one (on one-dimensional worlds) exists so far, but even that article is pretty thick with material, and perhaps interesting for many readers.