The worst case considered at the time was an uncontrolled chain-reaction annihilating the planet. It was calculated to be impossible, but it still weighed on th

The worst case considered at the time was an uncontrolled chain-reaction annihilating the planet. It was calculated to be impossible, but it still weighed on the minds of many scientists involved, even well into the hydrogen bomb era. https://www.insidescience.org/manhattan-project-legacy/atmosphere-on-fire https://www.insidescience.org/manhattan-project-legacy/atmos...