Comment by cratermoon

It's interesting that the article and the animations still lean on the concept of the proton having an "inside" with some kind of boundary. It makes for interesting animations, but that's not really a good way to understand anything at the quantum level. The particles and forces that make up a proton have probabilities of having certain features like momentum and velocity, and they are more likely to be within a certain area, but there's no "inside" for a charm quark to pop out of. The measurement that finds a charm quark/antiquark pair is just showing a certain state of the system that under standard conditions has a state we call a proton.