Examples on N-D arrays usage
They are very applicable in scientific computing. Right now, for instance, I am running simulations which output data in a 4D array: specifically 
| Time | x-position | y-position | z-position |.
Almost every modern spatial simulation will use multidimensional arrays,  along with programming for computer games.
I was surprised when I started learning numpy that there are N dimensional arrays. I'm a programmer and all I thought that nobody ever use more than 2D array. Actually I can't even think beyond a 2D array. I don't know how think about 3D, 4D, 5D arrays or more. I don't know where to use them.
Can you please give me examples of where 3D, 4D, 5D ... etc arrays are used? And if one used  numpy.sum(array, axis=5) for a 5D array would what happen?