## Six-dimensional spacetime

First consider the dual to Minkowski spacetime. Recall that the invariant interval of Minkowski spacetime has one dimension of time with three dimensions of space: (ds)² = (c dt)² – (dx1)² – (dx2)² – (dx3)² = (c dt)² – (dr)² where t is the time coordinate and x1, x2, and x3 are space coordinates of …