The study of the building blocks and interactions of atomic nuclei is known as nuclear physics.Nuclear physics is best recognized for its uses in nuclear power and nuclear weapons, but it also has applications in medical (nuclear medicine, magnetic resonance imaging), materials engineering (ion implantation), and archaeology (radiocarbon dating)..<br />Particle physics arose from nuclear physics and, as a result, has been referred to as such in the past.J. J. Thomson's discovery of the electron was the first evidence that the atom has internal structure.J. J. Thomson's "plum pudding" concept, in which the atom was a huge positively charged ball with little negatively charged electrons contained inside, was the accepted model of the atom at the turn of the twentieth century.Physicists had also found three forms of radiation emitted by atoms by the turn of the century, which they dubbed alpha, beta, and gamma radiation.Experiments by Lise Meitner and Otto Hahn in 1911, as well as James Chadwick in 1914, revealed that the<br />Rather than being discrete, the beta decay spectrum was continuous<br />That is, instead of the definite quantities of energy seen in gamma and alpha decays, electrons were released from the atom with a variety of energies.This was an issue for nuclear physics at the time since it showed that the energy in these decays was not conserved.In 1905, Albert Einstein formulated the idea of mass?energy equivalence. While the work on radioactivity by Becquerel, Pierre and Marie Curie predates this, an explanation of the source of the energy of radioactivity would have to wait for the discovery that the nucleus itself was composed of smaller constituents, the nucleons.<br />Rutherford’s team discovers the nucleus<br />In 1907 Ernest Rutherford published “Radiation of the a Particle from Radium in passing through Matter Geiger expanded on this work in a communication to the Royal Society with experiments he and Rutherford had done passing a particles through air, aluminum foil and gold leaf. More work was published in 1909 by Geiger and Marsden and further greatly expanded work was published in 1910 by Geiger,In 1911-2 Rutherford went before the Royal Society to explain the experiments and propound the new theory of the atomic nucleus as we now understand it.<br />