  In quantum mechanical experiments one distinguishes between the state of an
experimental system and an observable measured in it. Heuristically, the
distinction between states and observables is also suggested in scattering
theory or when one expresses causality. We explain how this distinction can be
made also mathematically. The result is a theory with asymmetric time evolution
and for which decaying states are exactly unified with resonances. A
consequence of the asymmetric time evolution is a beginning of time. The
meaning of this beginning of time can be understood by identifying it in data
from quantum jumps experiments.
