Home > Encyclopedia of Science > Nuclear Fusion

• Naturally occurring fusion reactions
• Words to Know
• Thermonuclear reactions
• Fusion reactions on Earth
• Peaceful applications of nuclear fusion
• Hope for the future
• Cold fusion

Nuclear fusion is the process by which two light atomic nuclei combine to form one heavier atomic nucleus. As an example, a proton and a neutron can be made to combine with each other to form a single particle called a deuteron. In general, the mass of the heavier product nucleus (the deuteron, for example) is less than the total mass of the two lighter nuclei (the proton and the neutron).

The mass that "disappears" during fusion is actually...