# Does the fact that protons and neutrons have larger mass than electrons mean they're bigger in size?

and so if a proton is so larger than an electron doesn't that mean it has a shape? What would be the shape of a subatomic particle? are they spherical?

• – jinawee Jan 31 '14 at 21:02

Does the fact that protons and neutrons have larger mass than electrons mean they're bigger in size?

No. The electron and muon are both believed to be "point-like" (which really means smaller than we can measure" despite having $\frac{m_\mu}{m_e} \approx 200$.

That is not to say the proton isn't bigger---it is---but that mass does not imply size in any simple way.

if a proton is so larger than an electron doesn't that mean it has a shape?

Yes. To date, not electric dipole moment has been observed which implies the proton is a sphere to high precision. (Probably I ought to say something about tensor form-factors here, but I'd be out of my depth.)

If string theory is correct, then the particles will be the shape of one-dimensional objects known as strings.

• Note that this is not true for composite objects like protons. – dmckee Feb 8 '14 at 20:12