A nuclear explosion occurs when a nuclear weapon detonates, releasing a massive amount of energy in the form of an explosion. This energy comes from nuclear reactions, either fission (splitting heavy atomic nuclei) or fusion (combining light atomic nuclei). The result is a powerful blast, intense heat, and radiation that can cause widespread destruction. The effects of a nuclear explosion can be devastating, leading to immediate loss of life and long-term environmental damage. Areas affected may experience radiation sickness, fires, and infrastructure collapse. The aftermath can also include long-lasting health issues for survivors and contamination of land and water, impacting ecosystems and human populations.