There are agents in Nature able to make the particles of bodies stick together by very strong attractions. ~ Isaac Newton
The strong force binds protons and neutrons in the nucleus of an atom. It is by far the strongest force: 100 times the tug of the electromagnetic force, 106 times that of the weak force, and 1039 times that of gravity. But then, the strong force applies only to irascible atomic nuclei, whereas gravity affects entire galaxies. The strength numeric is therefore an apples-and-oranges comparison, as the scales involved, while mathematically figurable, are practically incomparable.
Within the context of the Standard Model, the strong force is a gluon shotgun: forcing quarks to marry each other, and so form nucleons: the protons and neutrons which comprise atoms.
The strong force is overwhelming at distances the size of a nucleon (10–15 m): squeezing quarks together to form hadrons. It rapidly weakens beyond that range.
Protons are the only hadrons that are stable. All other hadrons, of which there are many, are ready prey to particle decay under sway of the weak force. Neutrons are stable only when inside atomic nuclei.
Protons nominally comprise 2 up quarks and 1 down quark, all different colors. Neutrons are 1 up quark and 2 down quarks, also different colors.
The weak force causes particle (beta) decay, a form of radioactivity, and initiates hydrogen fusion in stars. Under the Standard Model, the weak force is invoked by interaction between W± and Z0 bosons.
Weak interaction forces quarks to change flavor. Changing flavor means changing into a different type of quark.
As up and down quarks have the lowest mass, they are the most stable. Heavier quarks (strange, charm, bottom, and top) decay by weak interaction into a less energetic (massive) flavor.
The weak force also breaks the symmetry between matter and antimatter. While the strong force is about marriage, the weak force is about divorce.
A typical atomic nucleus has a spherical or watermelon profile, depending upon the nucleons within. But at high energies, nuclei become pear-shaped, as protons are pushed away from the center by an unknown force.
We’ve found these pear-shaped nuclei literally point toward a direction in space. This relates to a direction in time, proving there’s a well-defined direction in time and we will always travel from past to present.
Further, the protons enrich in the bump of the pear and create a specific charge distribution in the nucleus. This violates the theory of mirror symmetry and relates to the violation shown in the distribution of matter and antimatter in our universe. ~ Scottish nuclear physicist Marcus Scheck
Such asymmetry shows that there is yet another nuclear force besides strong and weak; one about which the Standard Model has nothing to say.