1. How is the size of an atom defined? Shouldn't it be the size of the universe? Is it defined as: The max span of an isolated electron cloud, such that the c.d.f. will equal .95? 2. How do we know force carriers/bosons exist? Have they been directly observed or are they just hypothesized to exist? 3. Since the proton is encapsulated within the electron cloud, I would assume that field is finite (at a certain radius there is a critical value where you can guarantee 100% that the proton will be in that region). Is this true?