You guys seriously need to stop thinking only in 4 dimensions. ;)
Space might seem empty to us because of our limited perception of the universe (we only have 5 senses), but as was pointed out before, space and all matter is composed out of Quantum Strings, so to be truly empty you'd need to look outside of our universe.
Time is just another form of distance, except it's the distance between two of the exact same points in space, just at different, well, times for lack of a better word. So without space, there's no time. Therefore talking about time before the big bang is meaningless.
What we see with our eyes isn't 4 dimensions; it's 3 dimensions, then 3 dimensions again a split second later... just like a movie is a series of still frames that look like they move when you play them fast enough. If you try to imagine 4 dimensions, (taking the Earth orbiting the sun for example) you wouldn't see the Earth moving around the sun, you would see the Earth at every point around the Sun simultaneously. It would look kind of like a tube around the sun, because you're now seeing multiple points in time simultaneously.
Now if you really want to make your brain explode, try imagining 5 dimensions. Personally I like to think of the 5th dimension as alternate realities. So now you're seeing the 4 dimensions you imagined earlier + the same thing, in the same space, in alternate timelines...
That's as far as my brain can go. I have no idea what 6 dimensions would look like, but I'm pretty sure I'd go insane if I ever managed to figure it out. :)