What is nuclear fusion?

Nuclear fusion refers to the process in which two lighter atomic nuclei combine to form a heavier nucleus, releasing a significant amount of energy in the process. This reaction occurs naturally in stars, including our sun, where hydrogen nuclei fuse to create helium and energy. The energy produced in fusion is vastly greater than that produced by nuclear fission, which involves splitting heavier nuclei.

Fusion requires extremely high temperatures and pressures to overcome the repulsive forces between the positively charged nuclei. Once these conditions are achieved, the nuclei can collide with enough energy to allow the nuclear force to unite them, resulting in a release of energy.

The other options describe different nuclear processes. The splitting of a nucleus pertains to fission, which is a different reaction where a heavier nucleus breaks apart into smaller nuclei. Radioactive decay involves the transformation of an unstable nucleus into a more stable configuration, often emitting radiation in the process. The transformation of thermal energy to kinetic energy is a separate concept related to thermodynamics, not directly relating to nuclear reactions.