Modeling of a system that is under constant change creates challenges that not not well understood.
Call it Induction, Correlation, Simulation or Modeling, the basic rule is to start with a system at equilibrium or Homeostasis so that the math is not too difficult. But real systems are never at equilibrium, those are all figments of the physicist's mind. Even when an equilibrium can be achieved in a laboratory, the question is still present. What exactly are we comparing reality to? Or, in other words, are we discussion auto- corelation or cross-correlation? Is the system self-similar or model of other other physical variable that might be nothing like. For example physicists equate black-holes with information theory or gas particles.