Nuclear fusion is the energy source of the future. It is what provides the sun and the stars with the energy to shine continuously for billions of years.
Fusion has been used here on earth to produce nuclear bombs, but has not yet been controlled so that we can obtain useful energy.
Fusion is what happens when two atomic nuclei are forced together by high pressure … high enough to overcome the strong repulsive forces of the respective protons in the nuclei. When the nuclei fuse, they form a new element, and release excess energy in the form of a fast-moving neutron. The energy is ‘extra’ because the mass of the newly formed nucleus is less than the sum of the masses of the original two nuclei; the extra mass is converted to energy according to Einstein’s equation E=mc2 This energy can be used to do useful work!