When I told my wife about our "discussion" she said she thinks your friend was talking about the "limited theorem" . This is part of differential equations in calculus and is the focus of probability study. Her most simple explanation that I could understand was this: two people facing each other 20 ft away. Each takes the exact two steps forward with the goal of eventually touching each other. As the data keeps track of the steps at some point it is virtually certain the subjects will touch each other and there is not need to actually observe the impact.