Strong interaction

In particle physics, the strong interaction is the mechanism responsible for the strong nuclear force (also called the strong force or nuclear strong force), and is one of the four known fundamental interactions, with the others being electromagnetism, the weak interaction, and gravitation.

Quotes

• In the case of the strong interactions, there was a wealth of experimental data, much of it of high precision. Hadronic masses and magnetic moments, nuclear binding energies and transition rates, many things were measured with great accuracy. But the strongly interacting world was so complicated that most of the experimental data was hard to interpret. Only a fraction of the experimental knowledge of strong interactions, such as the scaling behaviour in deep inelastic electron-nucleon scattering, gave simple clues about the underlying quark-gluon world. As a result, experimental clues alone did not suffice.
  • G. W. Gibbons; E. P. S. Shellard; S. J. Rankin (23 October 2003). The Future of Theoretical Physics and Cosmology: Celebrating Stephen Hawking's Contributions to Physics. Cambridge University Press. p. 455. ISBN 978-0-521-82081-3. 

• The strong force may not unify with the other forces. There’s no evidence for unification in our Universe so far, as proton decay experiments have come up empty. The initial motivation is flimsy here as well: If you put any three curves on a log-log scale and zoom out far enough, they will always look like a triangle where the three lines just barely miss coming together at a single point.
  • Ethan Siegel (12 February 2019). Why Supersymmetry May Be The Greatest Failed Prediction In Particle Physics History. forbes.com.