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I’m trying to work through the Ozma problem and the Wu experiment to get a better handle on parity and I’m being tripped up by something which is almost certainly trivial.

I can explain negative charge to aliens by saying heat up a gas, the stuff it emits is negatively charged.

I can say run a solenoid vertically with very cold Cobalt-60 in the middle. Run a current and define the current flow as being from +ve to ve- charge.

Here is my problem - to say which direction the Cobalt-60 spin will be oriented needs a sense of magnetic field orientation which requires the right hand rule and a consensus about which direction right is.

What do I say to the aliens about placing gamma ray and electron detectors to help them understand left from right? Is it - you’ll see more electrons emitted in the opposite direction of the current? If so how are they getting left/right out of it?

Qmechanic
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Learningthemath
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1 Answers1

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Probably the easiest approach is to describe the experiment as you normally would, using the cross product, which you define up to parity. Then they do the experiment and see which sign choice leads to a prediction that matches the data.

You could also say something along the lines of "if you were a decaying cobalt-60 nucleus, and were somersaulting forward, the direction you would preferentially emit the electron is your right", and let them figure out how to do the experiment. If they need help, you can present electromagnetism in a way that doesn't depend on the right-hand rule, using four-tensors for instance.

benrg
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