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Infinitely small, small and small question.  Does an electron have spatial extension?

Question asked by Mitsuru Yamada on May 22, 2014

I am asking you a question:  how large is the radius of an electron?  Though most of us cannot prove, we are compelled to believe that it has a spin.  Here I would like to quote from a book "Quantum man" written by Lawrence M. Krauss.


"...electrons possess a property called spin because they carry with them intrinsic "angular momentum", the property extended objects possess if they are spinning.  Classically no such concept exists for a point particle, which cannot behave as if it is spinning because there is no "center" (that is, another point) to spin around.  In order to have angular momentum, like a spinning bicycle wheel, for example, classical; objects must have spatial extension." (page 100, lines 6-14)


Does the radius of an electron have finite value still, or is it definitely zero?  Which is true?