Hi to everynoe! I have a bit of trouble in understanding the following thing : Suppose we have a phase space, in which a dynamical system evolves: for example a two dimensional vector space: temperature and time. Now, does it make a sense to define the euclidean norm of a vector in such space ? It just seems a bit strange to me to sum square seconds with square degrees and than extracting the square root. From the physical point of view it sould not have any sense... Well, perhaps some differential geometry topics are involved... Thanks four your help and attention.