Ok this is going to be hard for me to explain but I'll try my best. I'll include pics if I can be arsed.
Okay, first let's imagine a 1 dimensional world. It is affectively a line with no width that goes on to infinity.
From the top looking down.
http://img440.imageshack.us/img440/7956/1djx6.jpg
Okay. John (randon name) is the red dot that only exists in 1 dimension, for visibilty's sake I've drawn him as a circle. Those 2 blue dots looking out along the 'dimension' are his eyes they look along the black arrows. Imagine that a 2d shape from a 2d realm visits this 1d world. The 2d shape is a circle. So if you were to see a 2d circle passing through a 1d world it would appear to be a line that would start out as a dot, expand to be a line that is equal to the diameter of the circle, and then contract back to a dot again.
As shown in the pic (from side)
http://img405.imageshack.us/img405/7995/1ddiaag4.jpg
The green line is the part that the 1dimensional John can see and as you can see it increases and decreases as the 2d circle passes through the 1d world.
Okay, I hope you're still following as it get's slightly harder (for me anyway)
So now let us imagine a 2d world that looks like this:
http://img169.imageshack.us/img169/8348/2dwoldyb7.jpg
Again John can only see to the left and right, but now up and down also, as there is only 2 dimensions. It's like a 3d world but squashed paper thin... and then sat on. If we imagine an object from a 3d world were to pass through the 2d world I'll try and describe what it looks like. We'll use a sphere this time and please use your imaginations because spheres are hard to draw.
http://img105.imageshack.us/img105/3...diagramju5.jpg
Again the green line is the part that the 2d John can see.As the sphere passes through the 2d world it appears to be a circle that gets bigger and bigger until the diameter is equal to that of the sphere's diameter where it starts to decrease.
If in a 1d world a 2d circle appears as a line that gets bigger then smaller.
And in a 2d world a 3d sphere appears as a circle getting bigger then smaller.
So using these 2 facts imagine a 3d world i.e 'our world'.
Therefore in a 3d world a 4d 'circular based object?' (basically a sphere with 4 dimensions if you follow) would appear as a 3d sphere getting bigger and bigger until it is equal to the 4d sphere's 'diameter' where it starts to shrink.
To summarise: A 4d object, to us, would look like a sphere getting bigger and then getting smaller as it passes through are world.
I hope that explains it to you. oh and here's a diagram for you.
http://img119.imageshack.us/img119/9089/3dworldnz9.jpg
Well please comment on this topic as much as possible. I'll try very hard to answer some of your questions but please bear in mind I was born in (please look away now moderators) 1992. Please read the whole post before asking any questions. Oh and yes my paint skillz rock! Sorry for any typos I made. I'm not sure if this topic is right for philosophy but please don't delete it moderators as it took ages.