Comment by arter

A question that came to me as I was reading the article was - what makes us think that all protons are the same ? Can it be that instead of every proton having a superposition of 3 quarks, or 5 quarks or more, we have some protons with 3 and others with 5 ? How did they verify that this is not a case ? I am assuming they never managed to isolate 1 proton and test it twice.