Could a cobalt bomb actually turn the Earth into a lifeless, radioactive wasteland?

Countries & Cities · Published 3 October 2026 Swipe more like this →

In short: The cobalt bomb is a theoretical weapon designed to maximize radioactive fallout. While it has become a staple of doomsday fiction, from Dr. Strangelove to video games, there is no evidence that one has ever been built. It remains a chilling thought experiment about the limits of nuclear destruction.

The concept emerged in 1950 when physicist Leó Szilárd discussed it on the radio. His goal was not to advocate for such a device, but to illustrate that nuclear technology was advancing toward a point where a doomsday weapon could theoretically threaten all human life. A cobalt bomb functions by surrounding a thermonuclear weapon with ordinary cobalt-59. During the explosion, fusion neutrons transmute this metal into radioactive cobalt-60, which is then vaporized and dispersed as lethal fallout.

Unlike standard fission products, which decay relatively quickly, cobalt-60 has a half-life of 5.27 years. This duration is long enough to prevent survivors from waiting out the radiation in shelters, yet short enough to emit intense gamma radiation. However, the idea that such a bomb would universally sterilize the planet is considered fallacious. Fallout distribution is uneven, and the physics of neutron absorption means that converting 100% of the cobalt into its radioactive isotope is practically impossible.

Real-world experiments have yielded mixed results. A 1957 British test in Australia used cobalt pellets as a tracer, but it was deemed a failure due to low neutron absorption. Conversely, a 1971 Soviet nuclear test produced significant cobalt-60 from the steel surrounding the devices, leaving a lasting radioactive legacy. While modern fiction often depicts these weapons as city-killers, experts suggest that decontamination methods, such as removing contaminated topsoil, could mitigate the impact of such fallout, challenging the myth of an unstoppable, world-ending device.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

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