Why can you fire neutrons or alpha particles at the nucleus and see interesting nuclear effects but you can't fire electrons at the nucleus? Or can you? I would guess not, otherwise electrons would collapse into the nucleus in every day life. I've heard that doesn't happen because it would violate Heisenberg's Uncertainty Principle. If I accept that I can't see why HUP shouldn't forbid a neutron or alpha particle being fired at the nucleus. Is it to do with electrons being leptons?