Confinement — Gluing the Blocks Together
Why are quarks never alone? Counter to intuition, the force between them does not diminish
when there is distance between the quarks. The force is so strong that we must expend an
enormous amount of energy to try and pull the quarks apart. When the expended energy grows
large enough, a quark/anti-quark pair is created rather than letting the original quarks
separate (see illustration).
This property is called confinement. We observe this crucial phenomenon yet remain baffled by
its underlying cause. Understanding confinement is one of the most fundamental questions in
physics today. If quarks were not confined, the world would be a very different place.