15/06/2017
The Onion Madonna
- 1 of the 2 women awarded the Nobel Prize in Physics
At the end of World War II (1939-1945), Maria Goeppert Mayer attended the U.S. atomic bomb project and in 1948 she began with research on how atomic nuclei are built up, including the so-called "magic numbers" that had long puzzled scientists. After only a year she finds the solution!
Elements always have a nuclear charge, that is a specific number of protons, positively charged particles in the atom's nucleus. The number of neutrons, non-charged particles in the nucleus, can vary however. All these variations of the same element but with different numbers of neutrons are called isotopes. A stable isotope does not decompose with time, but retains the number of protons and neutrons intact.
In earlier experiments one had found that stable nuclei either have exactly 2, 8, 20, 28, 50, 82 and 126 protons - or exactly as many neutrons. These numbers were called the "magic numbers". But what made nuclei with “magic numbers” so stable?
“It was like a jigsaw puzzle. I had many pieces (not only the “magic numbers”), so I could see a picture began to emerge. I felt that if I had only one more piece of the puzzle, everything would fall into place. I found the piece, and everything became clear.”
The last piece in the puzzle was the discovery that protons and neutrons are spinning along orbits inside the atomic nucleus - in the same manner that earth spins around its own axis while moving in an orbit around the sun. The orbits in the atomic nuclei are like several shells, much like an onion with many shells but nothing in the center, Goeppert Mayer explained.
Her idea to liken the atomic nuclei with an onion made Wolfgang Pauli, also awarded the Nobel Prize in Physics, give her the nickname “The Onion Madonna”.
In August 1948, her first paper “On Closed Shells in Nuclei” summarizing the evidence for a shell model of the nucleus was published and the next paper on 15 June 1949 “On Closed Shells in Nuclei II”.
Her model was an important discovery in the development of nuclear physics.
