The violation-of-conservation-of-parity experiment that Wu came up with to test the Lee-Yang hypothesis is well described here:
> "The defining experiment involved cooling Cobalt-60 down to a hundredth of a degree Kelvin, a temperature at which its atoms can be induced to spin in one direction, and measure the number of electrons spun off from the top and bottom of the cobalt mass. If they are the same, then parity is conserved, since that way both the original cobalt atom and its opposite-spinning mirror copy will appear exactly the same. But, if one side emits more electrons than the other, parity would not be conserved, as whichever pole the atoms appear spewing from in the original, they will be spewing from the opposite pole in the mirror reflection, which would be like our clock hand stubbornly insisting on moving clockwise in spite of being reflected."
> "To test the hypothesis, Wu needed three things. The first was a nucleus that decayed due to weak force (beta decay). The second was that the nucleus must have an intrinsic quantum mechanical spin. The third and the tricky thing was that all the nuclei spins must be made to point in the same direction. So why is this?"
Richard Feynam wrote quite a bit about the Lee-Yang hypothesis on conservation of partity in weak decay processes and its experimental verification by Wu, that's where I first heard of it, symmetry in physical laws:
We seem to do a lot of cooling things down to near zero in physics. Is there something special about how things behave there? Or is it just basically a way to give us a slow motion view?
I think it's mostly eliminating random thermal motions that would otherwise swamp out the faint effects you're trying to measure, in this case such thermal effects would probably jiggle the cobalt atoms so much that they wouldn't line up properly.
Go low enough however and you do get strange quantum effect-related formation of Bose-Einstein condensates, and its even stranger newly discovered cousin, the Rydberg polaron:
> "The defining experiment involved cooling Cobalt-60 down to a hundredth of a degree Kelvin, a temperature at which its atoms can be induced to spin in one direction, and measure the number of electrons spun off from the top and bottom of the cobalt mass. If they are the same, then parity is conserved, since that way both the original cobalt atom and its opposite-spinning mirror copy will appear exactly the same. But, if one side emits more electrons than the other, parity would not be conserved, as whichever pole the atoms appear spewing from in the original, they will be spewing from the opposite pole in the mirror reflection, which would be like our clock hand stubbornly insisting on moving clockwise in spite of being reflected."
https://womenyoushouldknow.net/razor-sharp-physics-chien-shi...
Another good one:
> "To test the hypothesis, Wu needed three things. The first was a nucleus that decayed due to weak force (beta decay). The second was that the nucleus must have an intrinsic quantum mechanical spin. The third and the tricky thing was that all the nuclei spins must be made to point in the same direction. So why is this?"
https://www.secretsofuniverse.in/parity-violation-weak-exper...
Richard Feynam wrote quite a bit about the Lee-Yang hypothesis on conservation of partity in weak decay processes and its experimental verification by Wu, that's where I first heard of it, symmetry in physical laws:
https://www.feynmanlectures.caltech.edu/I_52.html
Of course, Feynman's lectures were delivered to an all-male audience at Caltech, which didn't allow women until 1970 or so, see the class:
https://physicstoday.scitation.org/na101/home/literatum/publ...
That issue has certainly greatly improved since then.