Catastrophe theory is the study of sudden, substantial and sometimes irreversible changes in the state of a system as it moves from a type of change which is continuous to one that is discontinuous. It is pictured by the action of a marble in a three dimensional landscape of peaks and valleys which may suddenly fall off the edge of a cliff. It has been described mathematically, using topological algebra. "Catastrophes" are characterized by the crossing of a threshold of stability such as the range of normal oscillation or the point at which incremental change in a certain direction gives way to abrupt change in another direction. The direction of the change is not necessarily unfavorable to the system; it may signal a significant opportunity as well as a potential disaster. Systems approach catastrophe through a region of instability from which they either return to equilibrium, or cross the boundary into a state in which they will either in turn find a new point of equilibrium or fail to survive. Systems can act to avert catastrophe by broadening the cusp of their zone of instability and giving themselves more time and space to recover from an disturbance. # SOURCE Thom, R. (1975). Structure, Stability and Morphogenesis. Reading, PA: Benjamin. For a popular treatment, see: Woodcock, A., & Davis, M. (1978). Catastrophe Theory. New York: E.P. Dutton. # EXAMPLES • a change from a fleeing to fighting mode of behavior in an animal • an avalanche • panic selling of stock • the declaration of war • the result of the addition of a crystal to a supersaturated solution • crossing a threshold of contamination which kills pond life • the number of available channels for radio and television • the neurological limits of human perception # NON-EXAMPLES • questions relating to the content of messages • whether or not the message is correctly addressed • explaining the theory of relativity on a single page or to a small child # PROBABLE ERROR • Choosing the wrong mode of communication for a message, • Choosing inappropriate transmitting conditions, • Not realizing that a given format or time and presentation delimits the complexity of the message, • Not allowing for distortion of the communication due to noise. # SEE Requisite Variety; Redundancy; Information