When the nuclei split, their neutrons could fly away at great speed, smashing into other nearby atoms, causing their nuclei to split in turn, releasing even more energy. If enough uranium atoms were gathered in the correct configuration—forming a critical mass—this process could begin sustaining itself, with one atom’s neutrons splitting the nucleus of another, sending more neutrons into a collision course with further nuclei. As it went critical, the resulting chain reaction of splitting atoms—nuclear fission—would liberate unimaginable quantities of energy.
