Consider the set of 4 × 4 matrices ? with real elements which satisfy the relation ? T g? = g , where g = ? ??? 1 0 0 0 0 ?1 0 0 0 0 ?1 0 0 0 0 ?1 ? ??? (1) is the metric tensor. These matrices represent Lorentz transformations of spacetime points (ct, x, y, z). (a) Under what conditions is a matrix of this set orthochronous? Explain what a non-orthochronous matrix represents physically.