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Spin Explained - Spin and Quantum Spin

Spin Explained - Spin and Quantum Spin

Spin is something we're all familiar with. We can make any object spin. And not just a top, spin is used to great effect in many sports such as tennis, baseball and cricket. And of course you could never throw a frisbee without spin.

We can spin an object at any speed we please, and as soon as it starts spinning it defines an axis about which the spin occurs.

But this is the spin of a big object, meaning an object we can handle. What about the spin of a really small object such as an electron?

It turns out the electron spins like a tiny top - but with two big surprises..

It spins at a fixed rate that can never be changed. There is no known process that can change the spin rate of the electron. This makes spin a fundamental quantity.

What about the axis of spin? You can measure the spin along any axis you want and you'll always get the same result, +1/2 or -1/2. It's like the electron is spinning about every axis at the same time!

Physicists call the electron a "spin 1/2 particle". And it's not just the electron, quarks have spin 1/2 and so do neutrinos. In fact all elementary particles have spin except for the recently discovered Higgs boson.

If you plan to study Quantum Mechanics pay attention to spin. It's not what you expect. And don't forget my instant summary of Quantum Mechanics, "small objects behave very differently than big objects". Spin is a superb example of this.

Content written and posted by Ken Abbott