How do fission and fusion release energy?

Fission and fusion release energy by converting mass into energy according to Einstein's equation, E=mc^2.

In nuclear fission, a heavy nucleus, such as uranium or plutonium, is split into two or more smaller nuclei, along with a few neutrons and a large amount of energy. This process is initiated by bombarding the heavy nucleus with a neutron. The resulting smaller nuclei have a combined mass that is less than the original heavy nucleus. This 'missing' mass has been converted into energy, which is released. This is in accordance with Einstein's mass-energy equivalence principle, E=mc^2, where E is energy, m is mass, and c is the speed of light.

Nuclear fusion, on the other hand, involves combining two light nuclei to form a heavier nucleus. This process, which powers the sun and other stars, also releases a large amount of energy. The most common fusion reaction in stars is the fusion of hydrogen to form helium. In this process, four hydrogen nuclei combine to form one helium nucleus. The mass of the helium nucleus is less than the combined mass of the four hydrogen nuclei. Again, the 'missing' mass has been converted into energy, which is released.

In both fission and fusion, the key to the release of energy is the principle of mass-energy equivalence. This principle, encapsulated in the equation E=mc^2, states that mass can be converted into energy, and vice versa. In fission, the mass of the original heavy nucleus is greater than the combined mass of the resulting smaller nuclei, and the 'missing' mass is converted into energy. In fusion, the combined mass of the original light nuclei is greater than the mass of the resulting heavier nucleus, and again, the 'missing' mass is converted into energy.