[evman150]

Yeah the flatlander thing is a common example. I remember reading about it in a couple of Sagan's books as well as Brian Greene's "The Elegant Universe". Greene's book is pretty ridiculous though, especially the second half. I feel I have a pretty good understanding of physics, but that book was just too much, especially for what was purportedly a "popular" book.

To give a brief explanation of the flatlander example for others in the thread, it works like this. Imagine you lived on a flat, 2d world where up and down didn't exist. Now say aliens from a third dimension came upon your world and threw a basketball down onto your 2d world. It landed right in front of you, what would you see? Well what you would see would be 2d "slices" of the 3d object. You would see the basketball first as a point, then as a small circle, then bigger circles, then achieving a maximum size of circle, then going back down to a point again then disappearing.

Pretty bizarre, it kind of gives you an idea of how weird the universe is when you realize this is how it is in our world, only scaled up one dimension. If 4d aliens came and threw a 4d object in front of me, all I would see would be consecutive 3d "slices" of the 4d object. It would be bizarre indeed. Of course this is just a thought experiment (there are no 4d aliens), but it gives one just a little better grasp of the whole 4d thing.