Here's some more cool stuff about dimensions. It's about real dimensions that are not really real (it's funny how the word real has different meanings in English).
Usually when we think about dimensions, they are integer numbers, like 3 for our regular space, and 4 if we include time to make it space-time.
In physics we sometimes have to compute infinitely long sums (integrals if you know calculus). Sometimes these sums in 4-dimensional space are infinite. That's not what we want.
We can fix this by making the dimension slightly less than 4, for instance 3.99, which is a real number (and not an integer). The infinite sums now splits nicely in a finite term, which is the answer we seek, and an infinite term that we trash.
Then, in the end, we let the dimension go almost back to 4, say 3.999999999999.
It's magic, isn't it? And what does it mean? It's just a math trick that let us do computations, nothing more and nothing less. The dimension of our real space-time is still 4 >:)
(The trick outlined above is called dimensional regularization. It was invented by the physicists t'Hooft and Veltman who won the Nobel Prize in 1999. I have no idea how to picture a 3.99 dimensional space, and there's no need to do it as long as the math works. The picture above is a 4-dimensional hypercube from Wikipedia)
