Lol, yeah, the 4th Dimension is time... though there are thought to be, according to string theory (wether this is true or not is yet to be
discovered) there could be up to 21 dimensions, though 10 dimensions is one of the more common notions... suprisingly the equations only work for set
numbers... but we can only see and experience 3 Dimensions (plus the fourth, time, but thats temporal rather than a spatial dimension) as the others
are thought to be "curled" up into a tiny space... so that they only exist on a size of subatomic length, thus we cannot see them. Some of the
larger particle colliders that are being made now should be able to test this theory pretty soon, if it's found then we could be in for some
interesting new technologies!
Anyway, I'm not very good at explaining things, had a quick trawl through the internet and found this
this.
Theres a lot of crap from people who don't know what they're on abou ton the net, but had a quick read through it and seems okay