Robert McNees
A team led by physicist Chien-Shiung Wu obtained the first experimental confirmation of parity violation in the decay of Cobalt-60, #OTD in 1956.
Her theory colleagues received a Nobel for predicting this phenomenon, but she was left off the prize.
Image: Smithsonian Institution Archives
Robert McNees
Scientists had long assumed parity — that physics proceeds by the same rules for a system and its mirror image — was a fundamental symmetry of Nature. That’s true for electromagnetism and the strong nuclear force, but not for the weak interaction associated with nuclear decays.
Robert McNees
Chien-Shiung Wu’s colleagues Chen Ning Yang and Tsung Dao Lee, the theorists who proposed the effect, were rightly awarded the Nobel Prize in 1957. She was left off the prize, of course. Another disappointing exclusion by the Nobel Committee.
At a 1964 MIT symposium, Chien-Shiung Wu commented: “I wonder whether the tiny atoms and nuclei, or the mathematical symbols, or the DNA molecules have any preference for either masculine or feminine treatment.”
Image: @Smithsonian Institution
Robert McNees
Last year the USPS issued stamps featuring Chien-Shiung Wu. And even though they did not use my proposal for the sheet, shown below, you should still buy some.
My arrangement of portraits on the sheet is just a joke meant to remind the viewer that parity is violated — there are more stamps facing one way than the other.
But the USPS sheet (with all portraits facing the same direction) is perhaps a better representation of parity violation in the weak nuclear force. Let me explain.
Robert McNees
When we say "parity is violated," it means that some physical process works differently under the sort of left-handed / right-handed swap you get in a mirror's reflection.
The weak nuclear force "maximally" violates parity, in that it only produces neutrinos that are (in a technical sense) left-handed, and never right-handed. This is why first signs of parity violation were first seen in nuclear decays mediated by the weak nuclear force.
Robert McNees
So in that sense, you can’t fault USPS for printing a sheet where all the stamps have Chien-Shiung Wu tilting her head slightly to the left.
https://store.usps.com/store/product/buy-stamps/chien-shiung-wu-S_480204
Incognitim
@mcnees
I was going to post a link the the Wu experiment wiki, buuut I think you've got that covered! Glad I fortuitously stumbled upon the rest of your great thread instead of just favouriting the first post and moving on! 🤓
Chirp! is a social network. It runs on GNU social, version 2.0.1-beta0, available under the GNU Affero General Public License.
All Chirp! content and data are available under the Creative Commons Attribution 3.0 license.