Nuclear physics is a branch of the physics field which is concerned with the structure of atomic nuclei, and the understanding of potential ways in which to manipulate atomic nuclei. This branch of physics dates to the early 20th century, when scientists began to realize that the atom had a structure, and that understanding this structure could be important. The most infamous application of nuclear physics was probably the development of the atom bomb in the 1940s, but the field has many more applications, including highly beneficial ones.
Some people group particle physics in with nuclear physics, although technically particle physics should be viewed as its own field. Particle physics is an offshoot of this field, but particle physicists take their research in very different directions, and work with different kinds of natural phenomena.
One of the most diverse applications of nuclear physics is in medicine. The work of nuclear physicists is behind a number of medical imaging techniques which are used to provide non-invasive looks into the body. Radioactive isotopes utilized in the treatment of some medical conditions such as cancer are also the product of research in nuclear physics, with physicists learning about such isotopes and how they can be applied safely and effectively to address medical problems.
Certain aspects of engineering require a knowledge of nuclear physics, most notably in nuclear engineering, a field which involves the development of nuclear power plants which can do anything from generating electricity to powering submarines. Radiocarbon dating, a technique used in geology and archeology, is also a product of nuclear physics. People in this profession may also work with astronomers, using their knowledge to help date the universe, explain physical phenomena, and design experiments. As seen from these examples, nuclear weapons represent only a small aspect of this field in physics.
People who are interested in careers in nuclear physics should plan on spending a lot of time in school. A physicist in this field generally gets a bachelor of science degree in physics, following this degree with graduate level work. Graduate work offers physicists a chance to develop an area of specialty, and to conduct research which may advance the field. Once qualified, a nuclear physicist can work in an academic setting, for a government agency, or for a private company, such as a company which offers radiocarbon dating services or runs nuclear power plants.