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Critical mass (sociodynamics)

In social dynamics, critical mass is a sufficient number of adopters of an innovation in a social system so that the rate of adoption becomes self-sustaining and creates further growth. The term is borrowed from nuclear physics and in that field it refers to the amount of a substance needed to sustain a chain reaction.

Social factors influencing critical mass may involve the size, interrelatedness and level of communication in a society or one of its subcultures. Another is social stigma, or the possibility of public advocacy due to such a factor.

Critical mass may be closer to majority consensus in political circles, where the most effective position is more often that held by the majority of people in society. In this sense, small changes in public consensus can bring about swift changes in political consensus, due to the majority-dependent effectiveness of certain ideas as tools of political debate.

Critical mass is a concept used in a variety of contexts, including physics, group dynamics, politics, public opinion, and technology.

The concept of critical mass was originally created by game theorist Thomas Schelling and sociologist Mark Granovetter to explain the actions and behaviors of a wide range of people and phenomenon. The concept was first established (although not explicitly named) in Schelling's essay about racial segregation in neighborhoods, published in 1971 in the Journal of Mathematical Sociology, and later refined in his book, Micromotives and Macrobehavior, published in 1978. He did use the term "critical density" with regard to pollution in his "On the Ecology of Micromotives". Mark Granovetter, in his essay "Threshold models of collective behavior", published in the American Journal of Sociology in 1978 worked to solidify the theory. Everett Rogers later cites them both in his important work Diffusion of Innovations, in which critical mass plays an important role.

The concept of critical mass had existed before it entered a sociology context. It was an established concept in medicine, specifically epidemiology, since the 1920s, as it helped to explain the spread of illnesses.