"Size" of elemetary particles I stumbled upon this nice link showing the universe at different scales: http://htwins.net/scale2/ However, if you scroll down to the attometer scale you get to the elementary particles which have been given sizes. Does anyone know what these sizes mean? I thought elementary particles were dimensionless and so have no strict size.
I'd guess it either refers to something similar to a "classical electron radius" or it uses their wavefunction to determine the volume of space they are likely to occupy and base the size on that.
You're correct. Apparently what he's diagramming here is the Compton wavelength for each particle, ħ/mc. Of the six quarks, the top quark has the greatest rest mass, hence the shortest Compton wavelength. Electron (classical) is the classical electron radius, e^{2}/mc^{2}.