Asymptotic freedom

Asymptotic freedom is a thing that happens with particles called quarks. Quarks normally stick together, but if they shake around fast enough (like if they're going really fast), they suddenly stop sticking together and can zoom away from each other. This is like if you had a rubber band and the more you stretch it, the looser and less sticky it gets. Quarks can do this fast enough that they can be really, really far apart in a really short amount of time. That's why it's called asymptotic freedom—like the quarks are becoming more and more free!