A key aspect of the theory is the explanation of why three out of four of the intermediary particles of the electroweak force are massive. (The photon is the massless one.) Unfortunately, the details ...A key aspect of the theory is the explanation of why three out of four of the intermediary particles of the electroweak force are massive. (The photon is the massless one.) Unfortunately, the details of why this is so are highly technical, so we cannot delve into this subject here. This is because the electromagnetic force between the charge of the electron and the charges on atomic nuclei are strong enough to rapidly cause the energy of the electron to be dissipated.