@code1949!134479 4D already exists. it has something to do with time.
4D exists, but it has nothing to do with time. our world is in 4-D and even in 5- and 6-D, the brain of the humans just can´t imagine it. All people think that our world is in 3-D and not more, but it isn't like this! 4-D is so complex that our brain can't imagine it and so we think it doesn't exist. 4-D is the hyperroom. You can think about 4-D but imagining it is so hard that you may get headache when you read this and try to imagine it. Well, we start on 3-D. 3-D is a geometric thing that is limited by 3 or more 2-D areas, which are limited by 3 or more 1-D lines themselves. Now, there is a cube which is limited by 6 cubes. This is real possible. A cube, which has 6 3-D cubes at its sides. This is 4-D. It's called Euklid's Hyperroomcube (i don't know, in german it's Euklidischer Hyperraumwürfel). http://en.wikipedia.org/wiki/Tesseract