The weak nuclear force is the cause of beta decay. It is 10^-13 (one-ten trillionth) as strong as the strong force. As a result the half life of most beta-decaying nuclei is long.

In 1968 Abdus Salam, Sheldon Glashow, and Steven Weinberg showed that the electromagnetic force and the weak nuclear force were actually different aspects of a single force, the electroweak force. How can these two forces that are so different in strength and range be unified? It only happens at extremely high energies (corresponding to a temperature of 10¹⁵ K), such as occurred in the first few moments after the Big Bang or in an accelerator. They received the 1979 Nobel Prize for their work.