ItвЂ™s in this context that the strong nuclear force traps (вЂњconfinesвЂќ) quarks, anti-quarks and gluons inside protons, neutrons and other вЂњhadronsвЂќ, such as pions. (вЂњStrongвЂќ is meant in a relative sense it is strong compared to the typical force at the same distance, as described here.) The strong nuclear force is strong when measured at distances comparable to or larger than the size of a proton (a millionth of a billionth of a meter) and in subatomic processes with energy much less than the E=mc 2 mass-energy of a proton.

The strong nuclear force, despite the name, isnвЂ™t always strong. But the topic today is somewhat different. The story begins with the strong nuclear force, whose connection with string theory IвЂ™ve written about before, for instance here and here. There are entirely unexpected phenomena that occur there, ones that we can look for in experiments. But then string theory drew our attention to this regime, and showed us that it has unusual features. ItвЂ™s a context that, until 1998 or so, no one had ever thought to ask about, and even if someone had, theyвЂ™d have been stymied because traditional methods are useless. The issue for today involves the behavior of particles in an unfamiliar context, one which might someday show up (or may already have shown up and been missed) at the LHC or elsewhere. These predictions have nothing to do with whether string theory will someday turn out to be the вЂњtheory of everything.вЂќ (ThatвЂ™s a grandiose term that means something far less grand, namely a вЂњcomplete set of equations that captures the behavior of spacetime and all its types of particles and fields,вЂќ or something like that itвЂ™s certainly not a theory of biology or economics, or even of semiconductors or proteins.) Such a theory would, presumably, resolve the conceptual divide between quantum physics and general relativity, EinsteinвЂ™s theory of gravity, and explain a number of other features of the world.В But to focus only on this possible application of string theory is to take an unjustifiably narrow view of its value and role. (Many people in my generation got caught in the crossfire.) But IвЂ™ve always taken the point of view that string theory is first and foremost a tool for understanding the universe, and it should be applied just like any other tool: as best as one can, to the widest variety of situations in which it is applicable.ДЄnd it is a powerful tool, one that most certainly makes experimental predictionsвЂ¦ even ones for the Large Hadron Collider (LHC). There have been various intellectual wars over string theory since before I was a graduate student. (An advanced particle physics topic todayвЂ¦)

The strings theory