What is Strong interaction?
The '''strong interaction''' or '''strong nuclear force''' is one of the four [[fundamental forces]] in [[physics]]. The other fundamental [[force]]s are [[electromagnetism]], the [[weak interaction]], and [[gravitation]]. They are called ''fundamental'' because there is no simpler way for [[physicist]]s to understand what the forces do or how they do it. The strong nuclear force is what holds most ordinary [[matter]] together. It does this in two ways: it holds [[subatomic particle]]s, like [[neutron]]s and [[protons]], together, and then it holds the [[atomic nucleus]] together. It is the strongest fundamental force—many times stronger than [[gravity]] (10<sup>38</sup> times stronger: that's 1 followed by 38 zeros). But it works only over very short distances of a few [[Metre|femtometre]]s (fm). A femtometre is 10<sup>−15</sup> (0.00000 00000 00001) metres. Scientists often think about the two ways the strong interaction works as separate forces: the '''color force''' and the '''nuclear force'''. At distances of 0.8 fm and less, the [[color force]]<!--redlink left but no page required--> holds [[hadron|subatomic particle]]s like [[protons]] and [[neutron]]s together. At distances of 1 to 3 fm, the residual (leftover) strong force is what keeps protons and neutrons together in the [[atomic nucleus]], so it is called the [[nuclear force]]. (This is like thinking of [[electricity]] and [[magnetism]] as separate forces, when the fundamental force is electromagnetism.) The strong interaction is often thought to be the action of [[gluon]]s, which 'glue' [[quark]]s together. Gluons can be exchanged (moved) between quarks, antiquarks and other gluons. All of those particles are said to carry a ''color charge'', something that some [[elementary particle]]s have which is like [[electric charge]]. Particles with color charge exchange gluons, like particles with electric charge exchange photons. The theory of [[quantum chromodynamics]] ('''QCD''') says that the strong force acts between [[quark]]s and [[gluon]]s. Qua