# Is a mobius strip spin 1/2 object?

1. Mar 4, 2004

### Sammywu

Remember Phiysicist always say electron has a spin of 1/2; I can't remember how it was derived?

But I noticed a mobius strip exihibit interesting attribute. Can we consider a mobius strip a spin 1/2 object?

2. Mar 4, 2004

### mathman

Electron spin 1/2 is an intrinsic quantum theory property. A mobius strip is a twisted piece of paper - it has nothing to do with quantum teory.

3. Mar 4, 2004

### GRQC

Well, a mobius strip is a non-orientable manifold, not a "twisted piece of paper". The obvious "connection" between the orientation of a unit normal vector on a mobius strip and 2-spinors (the representations of angular momentum states) is that they both require rotations of $$4\pi$$ to regain their original orientation.

So, mobius strip normal orientation and spinor rotations aren't that different.

Shouldn't this discussion be in the Quantum Physics subforum?

Last edited: Mar 4, 2004
4. Mar 4, 2004

### Mike H

As has been mentioned by many people before us, the entire spin-1/2 business falls out of relativistic Q.M.

The Mobius strip property is an analogy that is used in discussions of spin, at least pedagogically - I remember it being mentioned in undergraduate Q.M., as well as in the ever so delightful Principles of Magnetic Resonance by C.P. Slichter. It's intended to serve as a useful first step to understanding rotations.

5. Mar 4, 2004

### Sammywu

I thought my high school Physics teacher already showed us the spin 1/2 of electrons by examining its angular momentum against its light absortion spectrum.

That's why I thought this could be put in here as all it involves is rotation and angular momentum.

What you told me now is that the electrons' spins are more likely a QM quantity not related to a classical anugular rotation. I am not familiar with the modern QM at all. But didn't this spin 1/2 come originally from applying classical theory to the spectrum?

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