Giromagnetic Ratio: What is Spin & Meaning?

[decesicum]

What giromagnetic ratio means? What is exactly the spin (of an electron or proton)
Thanks for answering me.

 

[Meir Achuz]

The gyromagnetic ratio is defined as the ratio of the magnetic moment to the angular momentum. The electron and proton each have spin 1/2.
The electron has a gyromagnetic ratio 2X(e /2mc). The factor of 2 was a relativistic surprise, arising from the Dirac equation.
The proton's gyromagnetic ratio is 2X2.79X(e/2Mc). The additional factor of 2.79 is related to the "anamolous" magnetic moment of the proton due to its strong interactions.

 

[masudr]

And QED improves on Dirac's equation (not lessening the "magic" of his equation in any way) by quantizing the electromagnetic field.

This number (sometimes divided by two) is what one often states as "unprecedented agreement of theory and experiment," and in fact is probably the closest match between a theoretical and experimental figure in the history of science.