critical mass

critical mass (countable and uncountable, plural critical masses)

1. (nuclear physics) The amount of fissile material needed to support a self-sustaining nuclear chain reaction.
   • 2016, Carter Hydrick, Critical Mass […] ‎, third edition, TrineDay, →ISBN:

     […] Rhodes calculated the uranium bomb would eventually need “about 42 kilograms – 92.6 pounds,” which Rhodes then stated was approximately 2.8 critical masses. In other words, critical mass can be calculated to be about 15 kilograms.

2. (figurative) The tipping point.
   • 1993, Gerald Marwell; Pamela Oliver, The Critical Mass in Collective Action, Cambridge University Press, →ISBN, page 87:

     […] depending on the rare circumstance of there being a critical mass of persons whose combination of interests and resources is high enough to overcome the feasibility problem.

   • 2015, Giuseppe Riva; Brenda K. Wiederhold; Pietro Cipresso, editors, The Psychology of Social Networking, volume 1, Walter de Gruyter, →ISBN, page 204:

     The critical mass comprises the pioneers of an SNS who pay the start-up costs and set up a circle of acquaintances for newcomers; thereafter new subscribers to a mature SNS can join one after another rather than as a group (Heijden, 2004).

• subcritical mass
• supercritical mass

• critical mass on Wikipedia.Wikipedia