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A critical mass is a mass of fissile material that self-sustains a fission chain reaction. In this case, known as criticality , k = 1 . A steady rate of spontaneous fission causes a proportionally steady level of neutron activity.
In social dynamics, critical mass is a sufficient number of adopters of a new idea, technology or innovation in a social system so that the rate of adoption becomes self-sustaining and creates further growth. The point at which critical mass is achieved is sometimes referred to as a threshold within the threshold model of statistical modeling.
San Francisco Critical Mass, April 29, 2005. Critical Mass is a form of direct action in which people travel as a group on bicycles at a set location and time. The idea is for people to group together to make it safe for each other to ride bicycles through their streets, based on the old adage: there's safety in numbers.
In other words, in a critical mass, the number of neutrons emitted over time, exactly equals the number of neutrons captured by another nucleus or lost to the environment. If the mass is supercritical, the number of neutrons emitted per unit time exceeds those absorbed or lost, resulting in a cascade of nuclear fissions at increasing rate.
Criticality is the normal operating condition of a nuclear reactor, in which nuclear fuel sustains a fission chain reaction.A reactor achieves criticality (and is said to be critical) when each fission releases a sufficient number of neutrons to sustain an ongoing series of nuclear reactions.
The critical mass for any isotope is influenced by any impurities and the physical shape of the material. The shape with minimal critical mass and the smallest physical dimensions is a sphere. Bare-sphere critical masses at normal density of some actinides are listed in the accompanying table. Most information on bare sphere masses is ...
Immigration advocacy groups and Democratic leaders are seeking to disrupt President-elect Donald Trump's plan to deport millions of undocumented immigrants by pre-drafting lawsuits that could be ...
The Tipping Point: How Little Things Can Make a Big Difference is the debut book by Malcolm Gladwell, first published by Little, Brown in 2000. Gladwell defines a tipping point as "the moment of critical mass, the threshold, the boiling point."