Today's Sunday reflection:
"What about four-dimensional space? Is there such a thing? If we're asking whether four-dimensional space is real we might as well ask about three-dimensional space: Is there such a thing? I suppose it appears that there is. We're walking around (apparently), and things certainly look and feel as though they are part of a three-dimensional universe, but when you come right down to it, three-dimensional space is really an abstract mathematical object -- inspired by our perception of reality, to be sure, but imaginary nonetheless. So I don't think we should put four-dimensional space in any special mystical category. Spaces come in all sorts of dimensions, and none are any more real than any other. There are no one-dimensional or two-dimensional spaces in real life, and the only thing that gives the number 3 any special status is that our senses appear to offer us that particular illusion."
-- Paul Lockhart, from "Measurement"