X,Y,Z,i,t

The X and Y co-ordinates are the East and West co-ordinates.  We have a silly system with opposite directions.  Surely, West is Minus-East, and similarly for South.  The Z co-ordinate is obviously vertical height.  We are used to these two dimensional “maps” of the three dimensional world, where the Z dimension has been reduced to Zero everywhere.  Ironically considering the name is a co-incidence. 

Instead of just seeing the world in this flat way, we can imagine it with the Z dimension replaced by the “i” dimension, of the “unreal” numbers.  That way, electromagnetic radiation can propagate unseen and the mathematics used to design electronic circuits becomes sensible as well as useful.