1 2 Ja n 20 00 Forecast and event control : On what is and what cannot be possible

Consequences of the basic and most evident consistency requirement— that measured events cannot happen and not happen at the same time—are shortly reviewed. Particular emphasis is given to event forecast and event control. As a consequence, particular, very general bounds on the forecast and control of events within the known laws of physics are derived. These bounds are of a global, statistical nature and need not affect singular events or groups of events. Principle of self-consistency An irreducible, atomic physical phenomenon manifests itself as a click of some detector. There can either be a click or there can be no click. This yes-no scheme is experimental physics in-a-nutshell (at least according to a theoretician). From this type of elementary observation, all of our physical evidence is accumulated. Irreversibly observed events of physical reality (in the context in which they can be defined [1, 2, 3]) are subject to the primary condition of consistency or self-consistency. Any particular irreversibly observed event can either happen or cannot happen, but it must not both happen and not happen. Indeed, so trivial seems the requirement of consistency for the set of physically recorded events that David Hilbert polemicised against “another