Fusion

Nuclear fusion is where the nuclei of small atoms fuse together to form larger nuclei. This is how atoms are made. All atoms are created by the fusion of smaller atoms inside stars. When the star explodes these heavy atoms are dispersed into space. They may go on to form planets such as the Earth.

Every atom inside your body originated from nuclear fusion inside a star (except any hydrogen of course).

The most common fusion reaction inside our Sun is the fusion of hydrogen into helium.

The mass of the products of this reaction are slightly less than the mass of what we started with. The energy from the reaction comes from the conversion of mass into energy. The total mass of the Sun actually gets less by 400,000 tons a second.

Despite this it has been calculated that the Sun will last for a few more billion years.

Teams of scientists across the world are working very hard on trying to recreate nuclear fusion on a reasonable scale in a fusion reactor.