sentences:  In particular, Earth-based particle accelerators can produce particle interactions which are of much higher energy than are found in supernovae, but these experiments involve individual particles interacting with individual particles, and it is likely that the high densities within the supernova will produce novel effects.The interactions between neutrinos and the other particles in the supernova take place with the weak nuclear force, which is believed to be well understood.However, the interactions between the protons and neutrons involve the strong nuclear force, which is much less well understood.