Today is the birthday of physicist Wolfgang Pauli, born in Vienna, Austria in 1900. His brilliance showed early, as he published a paper on the then-new theory of relativity at age 18. He received his doctorate from the University of Munich in 1921, just as quantum mechanics was being developed. In 1925 Pauli proposed his famous exclusion principle, which states that no two electrons in an atom can be in the same state at the same time. In each electron-holding orbital, if one electron has spin +1/2, the other must have spin -1/2. The exclusion principle applies not only to electrons but to all fermions, which include protons and neutrons. Pauli later proposed the existence of electrically neutral particles called neutrinos; the particles were discovered in 1956, two years before his death. Pauli received the Nobel Prize in 1945 for his discovery of the exclusion principle.
