Also known as the weak interaction, it is one of the forces experienced by protons and neutrons in the nucleus of an atom, the other being the strong nuclear force. It is one of the four fundamental forces of physics (along with the gravitational force, the electromagnetic force and the strong nuclear force). It is called the weak force because it is about 1013 times weaker than the strong nuclear force and 1011times weaker than the electromagnetic force, and it is also very short range in its effect. The weak interaction is mediated by the exchange of heavy elementary particles known as W and Z bosons. It is responsible for radioactive beta decay (as it converts neutrons into protons) and for the production of neutrinos.