Doomsday device

Construct which could destroy all life on a planet or a planet itself

A doomsday device is a hypothetical construction — usually a weapon or weapons system — which could destroy all life on a planet, particularly Earth, or destroy the planet itself, bringing "doomsday", a term used for the end of planet Earth. Most hypothetical constructions rely on hydrogen bombs being made arbitrarily large, assuming there are no concerns about delivering them to a target or that they can be "salted" with materials designed to create long-lasting and hazardous fallout.

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