Originally posted by Sub_Mariner
If he has just learnt something, why will he forget it straight away?
"Nuclei are held together by strong interactions (mostly exchanging pions), but electromagnetic repulsion of the positively charged protons tends to push them apart, according to Coulomb's law. The stable nuclei all have close to the lowest energy ratio of protons to neutron for their atomic weight. Nuclei near enough to this ratio to be bound but not close enough to be stable, give off electrons or positrons (beta decay) or take in electrons (and also give off neutrinos), to move closer to that ratio. This is the main place where the weak interactions come in. Nuclei that are too massive to be stable are pulled apart by the coulomb repulsion of their protons and either fission or give off alpha particles."
Look at that for thirty seconds and then try to remember that.
Then look at two million times more information, and try to remember it all in same time.