Critical mass
Meaning
The minimum amount of something required to start or sustain a particular process or effect.
Origin
The phrase "critical mass" burst into public consciousness during the dawn of the nuclear age. Coined by physicists working on the Manhattan Project in the 1940s, it described the minimum amount of fissile material—like uranium-235 or plutonium-239—needed to sustain a nuclear chain reaction. Below this precise threshold, neutrons would simply escape, and the reaction would fizzle out; above it, an unstoppable cascade of nuclear fission would occur. This concept was the terrifying lynchpin of atomic bomb design, fundamentally linking the phrase to immense power and irreversible transformation. From its explosive scientific birth, "critical mass" swiftly escaped the laboratory, becoming a compelling metaphor for the point at which any process achieves unstoppable momentum.
Examples
- The startup needed to reach a critical mass of users before it could attract serious investors.
- For a social movement to succeed, it must gather a critical mass of supporters to create real change.