The strong nuclear force, also known as the strong interaction, is the fundamental force responsible for holding protons and neutrons together inside an atomic nucleus. It is the strongest of the four fundamental forces in nature, but it acts over a very short range—typically about the size of an atomic nucleus (~1 femtometer or 10⁻¹⁵ meters).
Inside the nucleus, protons repel each other due to their positive electric charge, which would naturally push them apart. However, the strong nuclear force overcomes this repulsion and binds them tightly to each other and to the neutrons, which are electrically neutral.
This force operates between quarks, the fundamental constituents of protons and neutrons. It is mediated by particles called gluons, which constantly exchange between quarks and bind them together inside nucleons. At the nucleon level (protons and neutrons), the strong force is experienced as a residual force that keeps these particles bound in the nucleus.
Without the strong nuclear force:
- Atomic nuclei would not exist,
- Atoms would not form,
- The universe as we know it—matter, stars, planets—would not exist.
It also plays a central role in nuclear reactions, such as fusion in stars and fission in nuclear reactors, releasing enormous amounts of energy. Thus, the strong nuclear force is a vital force that sustains matter and powers the stars.