参考答案 :)

"If we love in the other world as we do in this (world), I shall love thee to eternity."

Imagine you are at the origin of a time-space coordinates, your "this world" would be one point at the origin.  If the event (act of love) may be transposed to any other point (other world) in the coordinates without change (as we do in this world), then the event is univeral through out (eternity).  Therefore the world should be "时空", eh?