ABSTRACT
The first observations of weak interactions were made by accident in 1896, when Henri Bequerel was investigating phosphorescence, the phenomenon in which certain materials glow in the dark after exposure to light. Radioactive decay will change one nucleus to another whenever the binding energy of the product nucleus is larger than that of the initial decaying nucleus. A magnetic field was found to split radioactive emissions into three types of beams: alpha, beta and gamma. The alpha rays were seen to carry a positive charge, beta rays a negative charge, and gamma rays were neutral. Pauli suggested that there was a very light, uncharged, and penetrating particle that he called the neutron, two years before Chadwick’s discovery. It is possible to get bounds on neutrino mass from cosmological observations. Neutrinos with masses of only a few tenths of an electron volt can significantly influence the formation of large-scale structures in our universe.
