Strong and Weak Force

Claimed by JAMES SOULE (Spring 2026)

Strong and Weak forces are nuclear forces that govern subatomic behavior in our universe.

Strong and Weak forces are two of the four fundamental forces, with the other two being gravity and the Electromagnetic Force. This article will serve as an overview of the concepts, applications, and history of Strong and Weak forces.

Strong Force

The Strong Force binds the nucleus together, and is the strongest force in the universe. It is [math]\displaystyle{ 10^{38} }[/math] times stronger than the force of gravity, operates at a scale of [math]\displaystyle{ 10^{-15} m }[/math], and is 137 times stronger than the electromagnetic force. While this force holds together protons and neutrons to create a nucleus, it also is responsible for holding together the quarks that make up those subatomic particles in the nucleus. We specify that this force is keeping together quarks in the nucleus, since electrons that are outside the nucleus are not made of quarks, and therefore not held together by the Strong Force.

However, the strong force requires a medium particle (also called an exchange particle), known as gluons.

Weak Force

The weak nuclear force, despite its name, is [math]\displaystyle{ 10^{31} }[/math] times stronger than the force of gravity, but operates at a short range. Controlling interactions on a scale of [math]\displaystyle{ 10^{-17} m }[/math], it is 100x shorter than the range of the Strong Force. The Weak Force's main interaction with the nucleus is "flipping" a proton into a neutron, and vice versa. When a neutron "flips" into a proton, the element changes, but the mass of atom stays the same. In this flipping process, an electron will be emitted to counteract the proton's charge.

History

Finding the Strong Force:

• 1935: Hideki Yukawa proposed the existence of "mesons"—intermediate-mass particles—that acted as the exchange medium for a new force that held nucleons together. This idea was used to develop later theories about the forces binding the atom.

• 1970s: Eventually an understanding of Quantum Chromodynamics allowed us to analyze fundamental forces in the atom by analyzing the color charge of quarks by their gluons, which emit an analyzable color.

Understanding Beta Decay

• 1935: Enrico Fermi proposed his theory of Beta Decay to explain how atoms changed identity. It proposed how a force can cause a neutron to flip, and produce an electron. However, he had no way to physically prove this.

• 1956: It was not until the Cowan–Reines Neutrino Experiment that there was physical proof of Fermi's theories. This was the discovery of Neutrinos, and proves the "invisible" part of Fermi's theories to be real.