I think hansda got confused a few lines above the one I just quoted: I think hansda saw that completely unsourced line about the Penning traps (which appears to be talking in terms of classical physics anyway), and ran with it. In doing so, (s)he forgot to read the rest of that section, where it clearly explains it's an unsettled issue. Edit: Interestingly enough, there's similar discussions on the talk page: https://en.wikipedia.org/wiki/Talk:Electron#Radius https://en.wikipedia.org/wiki/Talk:...g_"caused_by"_virtual_photons,_"causes"_spin? But there too, the statement is unsourced. Edit2: Yes, it's a fully unsourced addition: https://en.wikipedia.org/w/index.php?title=Electron&diff=prev&oldid=633949990 Thus it can safely be disregarded.